Use return code to determine service status in Upstart module.

This also broke the "dead" state.

This is because `service` will call `/etc/init.d/<service-name>` for
System V style services. Each of which could have different output.

For example:

    $ sudo invoke-rc.d exim4 stop
     * Stopping MTA                                               [ OK ]
    $ sudo service exim4 status
     * checking separate queue runner daemon...                   [ OK ]
     * checking combined SMTP listener and queue runner daemon... [ OK ]
    $ echo $?
    3
    $ sudo invoke-rc.d exim4 start
     * Starting MTA                                               [ OK ]
    $ sudo service exim4 status
     * checking separate queue runner daemon...                   [ OK ]
     * checking combined SMTP listener and queue runner daemon... [ OK ]
    $ echo $?
    0

salt/modules/upstart.py

@@ -221,7 +221,7 @@ def status(name, sig=None):
         salt '*' service.status <service name>
     '''
     cmd = 'service {0} status'.format(name)
-    return 'start/running' in __salt__['cmd.run'](cmd)
+    return not bool(__salt__['cmd.retcode'](cmd))
 
 
 def _get_service_exec():