tests: Make coins_tests/updatecoins_simulation_test deterministic #16225

Make coins_tests/updatecoins_simulation_test deterministic.

Before:

$ contrib/devtools/test_deterministic_coverage.sh 1000
[2019-06-15 05:36:20] Measuring coverage, run [#1](/bitcoin-bitcoin/1/) of 1000
[2019-06-15 05:38:05] Measuring coverage, run [#2](/bitcoin-bitcoin/2/) of 1000
[2019-06-15 05:39:49] Measuring coverage, run [#3](/bitcoin-bitcoin/3/) of 1000
[2019-06-15 05:41:38] Measuring coverage, run [#4](/bitcoin-bitcoin/4/) of 1000
[2019-06-15 05:43:16] Measuring coverage, run [#5](/bitcoin-bitcoin/5/) of 1000
...
[2019-06-16 18:25:23] Measuring coverage, run [#880](/bitcoin-bitcoin/880/) of 1000
[2019-06-16 18:27:12] Measuring coverage, run [#881](/bitcoin-bitcoin/881/) of 1000
[2019-06-16 18:29:33] Measuring coverage, run [#882](/bitcoin-bitcoin/882/) of 1000
[2019-06-16 18:33:00] Measuring coverage, run [#883](/bitcoin-bitcoin/883/) of 1000
[2019-06-16 18:35:32] Measuring coverage, run [#884](/bitcoin-bitcoin/884/) of 1000

The line coverage is non-deterministic between runs. Exiting.

The test suite must be deterministic in the sense that the set of lines executed at least
once must be identical between runs. This is a necessary condition for meaningful
coverage measuring.

--- gcovr.run-1.txt     2019-06-15 05:38:05.282359029 +0200
+++ gcovr.run-884.txt   2019-06-16 18:37:23.518298374 +0200
@@ -269,7 +269,7 @@
 test/bloom_tests.cpp                         320     320   100%   
 test/bswap_tests.cpp                          13      13   100%   
 test/checkqueue_tests.cpp                    223     222    99%   169
-test/coins_tests.cpp                         478     472    98%   52,68,344-345,511,524
+test/coins_tests.cpp                         478     474    99%   52,68,511,524
 test/compilerbug_tests.cpp                    18      18   100%   
 test/compress_tests.cpp                       27      27   100%   
 test/crypto_tests.cpp                        268     268   100%   
@@ -401,5 +401,5 @@
 zmq/zmqpublishnotifier.h                       5       0     0%   12,31,37,43,49
 zmq/zmqrpc.cpp                                23       3    13%   16,18,20,23,33-35,37,40-47,51,62,64-65
 ------------------------------------------------------------------------------
-TOTAL                                      53323   28305    53%
+TOTAL                                      53323   28307    53%
 ------------------------------------------------------------------------------

After:

$ contrib/devtools/test_deterministic_coverage.sh 1000
[2019-06-15 05:36:20] Measuring coverage, run [#1](/bitcoin-bitcoin/1/) of 1000
[2019-06-15 05:38:05] Measuring coverage, run [#2](/bitcoin-bitcoin/2/) of 1000
[2019-06-15 05:39:49] Measuring coverage, run [#3](/bitcoin-bitcoin/3/) of 1000
[2019-06-15 05:41:38] Measuring coverage, run [#4](/bitcoin-bitcoin/4/) of 1000
[2019-06-15 05:43:16] Measuring coverage, run [#5](/bitcoin-bitcoin/5/) of 1000
...
$

ACK f8995807e4f08fd0266899e3e227903f06da6ab1 (checked that the randomness state of g_insecure_rand_ctx is the same after three test runs)

<details><summary>Show signature and timestamp</summary>

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ACK f8995807e4f08fd0266899e3e227903f06da6ab1 (checked that the randomness state of g_insecure_rand_ctx is the same after three test runs)
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Timestamp of file with hash 2488b0f07eaf701b85ba2ada131d501c865e3c2cfd81b08cd0cb4180ed9f9e6f -

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