test: Fix off-by-one in mockscheduler test RPC #21948

Fixes:

fuzz: scheduler.cpp:83: void CScheduler::MockForward(std::chrono::seconds): Assertion `delta_seconds.count() > 0 && delta_seconds < std::chrono::hours{1}' failed.
==1059066== ERROR: libFuzzer: deadly signal
    [#0](/bitcoin-bitcoin/0/) 0x558f75449c10 in __sanitizer_print_stack_trace (/root/fuzz_dir/scratch/fuzz_gen/code/src/test/fuzz/fuzz+0x5fec10)
    [#1](/bitcoin-bitcoin/1/) 0x558f753f32b8 in fuzzer::PrintStackTrace() fuzzer.o
    [#2](/bitcoin-bitcoin/2/) 0x558f753d68d3 in fuzzer::Fuzzer::CrashCallback() fuzzer.o
    [#3](/bitcoin-bitcoin/3/) 0x7f4a3cbbb3bf  (/lib/x86_64-linux-gnu/libpthread.so.0+0x153bf)
    [#4](/bitcoin-bitcoin/4/) 0x7f4a3c7ff18a in raise (/lib/x86_64-linux-gnu/libc.so.6+0x4618a)
    [#5](/bitcoin-bitcoin/5/) 0x7f4a3c7de858 in abort (/lib/x86_64-linux-gnu/libc.so.6+0x25858)
    [#6](/bitcoin-bitcoin/6/) 0x7f4a3c7de728  (/lib/x86_64-linux-gnu/libc.so.6+0x25728)
    [#7](/bitcoin-bitcoin/7/) 0x7f4a3c7eff35 in __assert_fail (/lib/x86_64-linux-gnu/libc.so.6+0x36f35)
    [#8](/bitcoin-bitcoin/8/) 0x558f7588a913 in CScheduler::MockForward(std::chrono::duration<long, std::ratio<1l, 1l> >) scheduler.cpp:83:5
    [#9](/bitcoin-bitcoin/9/) 0x558f75b0e5b1 in mockscheduler()::$_7::operator()(RPCHelpMan const&, JSONRPCRequest const&) const rpc/misc.cpp:435:30
    [#10](/bitcoin-bitcoin/10/) 0x558f75b0e5b1 in std::_Function_handler<UniValue (RPCHelpMan const&, JSONRPCRequest const&), mockscheduler()::$_7>::_M_invoke(std::_Any_data const&, RPCHelpMan const&, JSONRPCRequest const&) /usr/bin/../lib/gcc/x86_64-linux-gnu/9/../../../../include/c++/9/bits/std_function.h:285:9
    [#11](/bitcoin-bitcoin/11/) 0x558f7587a141 in std::function<UniValue (RPCHelpMan const&, JSONRPCRequest const&)>::operator()(RPCHelpMan const&, JSONRPCRequest const&) const /usr/bin/../lib/gcc/x86_64-linux-gnu/9/../../../../include/c++/9/bits/std_function.h:688:14
    [#12](/bitcoin-bitcoin/12/) 0x558f7587a141 in RPCHelpMan::HandleRequest(JSONRPCRequest const&) const rpc/util.cpp:565:26
    [#13](/bitcoin-bitcoin/13/) 0x558f756c0086 in CRPCCommand::CRPCCommand(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, RPCHelpMan (*)())::'lambda'(JSONRPCRequest const&, UniValue&, bool)::operator()(JSONRPCRequest const&, UniValue&, bool) const ./rpc/server.h:110:91
    [#14](/bitcoin-bitcoin/14/) 0x558f756c0086 in std::_Function_handler<bool (JSONRPCRequest const&, UniValue&, bool), CRPCCommand::CRPCCommand(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, RPCHelpMan (*)())::'lambda'(JSONRPCRequest const&, UniValue&, bool)>::_M_invoke(std::_Any_data const&, JSONRPCRequest const&, UniValue&, bool&&) /usr/bin/../lib/gcc/x86_64-linux-gnu/9/../../../../include/c++/9/bits/std_function.h:285:9
    [#15](/bitcoin-bitcoin/15/) 0x558f756b8592 in std::function<bool (JSONRPCRequest const&, UniValue&, bool)>::operator()(JSONRPCRequest const&, UniValue&, bool) const /usr/bin/../lib/gcc/x86_64-linux-gnu/9/../../../../include/c++/9/bits/std_function.h:688:14
    [#16](/bitcoin-bitcoin/16/) 0x558f756b8592 in ExecuteCommand(CRPCCommand const&, JSONRPCRequest const&, UniValue&, bool) rpc/server.cpp:480:20
    [#17](/bitcoin-bitcoin/17/) 0x558f756b8592 in ExecuteCommands(std::vector<CRPCCommand const*, std::allocator<CRPCCommand const*> > const&, JSONRPCRequest const&, UniValue&) rpc/server.cpp:444:13
    [#18](/bitcoin-bitcoin/18/) 0x558f756b8017 in CRPCTable::execute(JSONRPCRequest const&) const rpc/server.cpp:464:13
    [#19](/bitcoin-bitcoin/19/) 0x558f7552457a in (anonymous namespace)::RPCFuzzTestingSetup::CallRPC(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::vector<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::allocator<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > > const&) test/fuzz/rpc.cpp:50:25
    [#20](/bitcoin-bitcoin/20/) 0x558f7552457a in rpc_fuzz_target(Span<unsigned char const>) test/fuzz/rpc.cpp:354:28
    [#21](/bitcoin-bitcoin/21/) 0x558f7544cf0f in std::_Function_handler<void (Span<unsigned char const>), void (*)(Span<unsigned char const>)>::_M_invoke(std::_Any_data const&, Span<unsigned char const>&&) /usr/bin/../lib/gcc/x86_64-linux-gnu/9/../../../../include/c++/9/bits/std_function.h:300:2
    [#22](/bitcoin-bitcoin/22/) 0x558f75c05197 in std::function<void (Span<unsigned char const>)>::operator()(Span<unsigned char const>) const /usr/bin/../lib/gcc/x86_64-linux-gnu/9/../../../../include/c++/9/bits/std_function.h:688:14
    [#23](/bitcoin-bitcoin/23/) 0x558f75c05197 in LLVMFuzzerTestOneInput test/fuzz/fuzz.cpp:74:5
    [#24](/bitcoin-bitcoin/24/) 0x558f753d8073 in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) fuzzer.o
    [#25](/bitcoin-bitcoin/25/) 0x558f753c1f72 in fuzzer::RunOneTest(fuzzer::Fuzzer*, char const*, unsigned long) fuzzer.o
    [#26](/bitcoin-bitcoin/26/) 0x558f753c7d6a in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) fuzzer.o
    [#27](/bitcoin-bitcoin/27/) 0x558f753f3a92 in main (/root/fuzz_dir/scratch/fuzz_gen/code/src/test/fuzz/fuzz+0x5a8a92)
    [#28](/bitcoin-bitcoin/28/) 0x7f4a3c7e00b2 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x270b2)
    [#29](/bitcoin-bitcoin/29/) 0x558f7539cc9d in _start (/root/fuzz_dir/scratch/fuzz_gen/code/src/test/fuzz/fuzz+0x551c9d)

Can also be tested by typing mockscheduler 3600

<!--e57a25ab6845829454e8d69fc972939a-->

The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.

<!--174a7506f384e20aa4161008e828411d-->

Conflicts

Reviewers, this pull request conflicts with the following ones:

• #21538 (fuzz: Add fuzzing syscall sandbox: detect use of unexpected syscalls when fuzzing ("syscall sanitizer") by practicalswift)
• #20487 (Add syscall sandboxing using seccomp-bpf (Linux secure computing mode) by practicalswift)

If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

Nice to see the RPC fuzzer find bugs :)

cr ACK fa2e614d16af84327adf1c02746d0f73e0f48111