Prior to this commit, in case an RPC failure occurred when
accesing the block height, the program would continue but the
wallet would be in an un-writeable state (for command line
programs, specifically yield generators; for Qt the shutdown
would occur).
This commit slightly cleans up the process of shutting down,
ensuring that duplicate shutdown calls do not result in
stack traces. It also ensures that also for command line
programs, the application will immediately shutdown if the
regular heartbeat call to query the block height fails, as this
risks inconsistencies in the wallet (though the previous
situation luckily did not result in this as the call to
BaseWallet.close() resulted in the wallet being read only).
A future PR should develop a more sophisticated approach to
RPC call failures that may allow the program to wait.
stopservice
Adam Gibson
a2aafd254d