zulip_tools: Find missing processes/groups in list_supervisor_processes.
zulip_tools: Find missing processes/groups in list_supervisor_processes.

Nonexistent processes and groups passed to `supervisortctl status` are
printed to STDOUT as follows:

```
$ supervisorctl status zulip-django nonexistent-process nonexistent-group:*
nonexistent-process: ERROR (no such process)
nonexistent-group: ERROR (no such group)
zulip-django                     RUNNING   pid 16043, uptime 17:31:31
```

On supervisor 4 and above, this exits with an exit code of 4;
previously, it returned exit code 0.  Ubuntu 18.04 has version 3.3.1,
and Ubuntu 20.04 has version 4.1.0.

Skip any lines with `ERROR (no such ...)`, and accept exit code 4 from
`supervisorctl status`.

eeshangarg/zulip,andersk/zulip,zulip/zulip,hackerkid/zulip,punchagan/zulip,rht/zulip,punchagan/zulip,zulip/zulip,eeshangarg/zulip,hackerkid/zulip,kou/zulip,andersk/zulip,kou/zulip,eeshangarg/zulip,rht/zulip,kou/zulip,punchagan/zulip,rht/zulip,hackerkid/zulip,zulip/zulip,eeshangarg/zulip,rht/zulip,andersk/zulip,rht/zulip,eeshangarg/zulip,hackerkid/zulip,kou/zulip,andersk/zulip,rht/zulip,punchagan/zulip,rht/zulip,andersk/zulip,kou/zulip,hackerkid/zulip,eeshangarg/zulip,zulip/zulip,zulip/zulip,punchagan/zulip,punchagan/zulip,hackerkid/zulip,punchagan/zulip,zulip/zulip,hackerkid/zulip,zulip/zulip,andersk/zulip,andersk/zulip,kou/zulip,eeshangarg/zulip,kou/zulip