Fixes#1166.
Fixes#1173.
Prior to this commit, in tests, we were calling
JMWalletDaemon.stopService at exit of the python script,
outside the pytest context, leading to various errors because
the test framework had gone through tear down.
After this commit, no attempt to call stopService is made
at exit (this is not necessary, we already call wallet close
and there is no other persistence necessary).