test: Use one node to avoid a race due to missing sync in rpc_signrawtransaction #18543

Node 0 creates a transaction in a block, and node 1 sends a spending transaction without properly syncing the utxo set.

Fixes intermittent test failure in rpc_signrawtransaction

test  2020-04-01T00:14:03.400000Z TestFramework (ERROR): JSONRPC error 
                                   Traceback (most recent call last):
                                     File "C:\projects\bitcoin\test\functional\test_framework\test_framework.py", line 112, in main
                                       self.run_test()
                                     File "C:\projects\bitcoin/test/functional/rpc_signrawtransaction.py", line 213, in run_test
                                       self.witness_script_test()
                                     File "C:\projects\bitcoin/test/functional/rpc_signrawtransaction.py", line 208, in witness_script_test
                                       self.nodes[1].sendrawtransaction(spending_tx_signed['hex'])
                                     File "C:\projects\bitcoin\test\functional\test_framework\coverage.py", line 47, in __call__
                                       return_val = self.auth_service_proxy_instance.__call__(*args, **kwargs)
                                     File "C:\projects\bitcoin\test\functional\test_framework\authproxy.py", line 141, in __call__
                                       raise JSONRPCException(response['error'], status)
                                   test_framework.authproxy.JSONRPCException: bad-txns-inputs-missingorspent (-25)

Full log: https://ci.appveyor.com/project/DrahtBot/bitcoin/builds/31864368

cc @achow101

I think the same is needed above on line 189. Or maybe just change these to self.nodes[0]?

Switched both to node[0] as suggested by @achow101

ACK fa2251df5e3471e0d19d5d5c7780d34ee1498cee