glob returns wildcard pattern when no pids have been found

### Description
Status command isn't usable when no workers are running.

### Expected results
Script should give a message about stopped service

### Actual results
Script fails with following message
```
cat: /var/run/celery/*.pid: No such file or directory                                                                 │85597 nobody        1  20    0   228M  2924K kqread 23   1:11  0.00% nginx
bad pid file (/var/run/celery/*.pid) 
```