Add working status detection for pf on FreeBSD

The return code of "service pf onestatus" is usually zero on FreeBSD (tested with FreeBSD 10.0), even if pf is not running. So the service module always thinks that pf is running, even when it needs to be started.

lib/ansible/modules/system/service.py

@@ -928,6 +928,9 @@ class FreeBsdService(Service):
 
     def get_service_status(self):
         rc, stdout, stderr = self.execute_command("%s %s %s %s" % (self.svc_cmd, self.name, 'onestatus', self.arguments))
+        if self.name == "pf":
+            self.running = "Enabled" in stdout
+        else:
             if rc == 1:
                 self.running = False
             elif rc == 0: