Fixed Control-C race.

Fixed Control-C race.

A typo in kill_console() could cause the application to be restarted
when it was supposed to stop.

When kill_console() successfully generated a Control-C event and the
application exited, the function was supposed to return 0, indicating to
its parent function kill_process() that the application had been killed.

Due to a mistake in the test of WaitForSingleObject()'s return code,
kill_console() would instead return non-zero when the application exited
in response to Control-C.  This would lead NSSM to continue with other
methods of trying to kill the application, leading to a race when
another thread detected that the application had exited without
recognising that it had done so in response to a stop control.

Thanks Barrett Lewis.