Not all exit paths remove the pid file

[fluca1978]

In the main there are some exit conditions, e.g., due to not being able to bind a socket, that perform an exit(1) without removing the pid file (e.g., https://github.com/agroal/pgagroal/blob/master/src/main.c#L1036). All the exit paths should be unified to remove the pid file, otherwise the next time the application is started it will complain about the pid file being there.