Fix exit status of "/etc/init.d/supervisord status" under rhel.

Prior to this change, under CentOS for example, the service[supervisord]
resource could think that supervisord was running even when it wasn't.
This is because under CentOS (and possibly other platforms), "supervisorctl
status" exits with status 0 even when supervisord is not running:

    $ supervisorctl status
    unix:///var/run/supervisor.sock no such file
    $ echo $?
    0