Fix starting of coturn-synapse service

[tituspijean]

Problem

@kavelach in the chatroom experiences an issue while starting the CoTURN server:

 coturn-synapse.service: Can't open PID file /run/coturn-synapse/turnserver.pid (yet?) after start: Operation not permitted.

Solution

• PIDFile option in service conf file implies that Systemd will remove the file when the service is stopped. No need for the ExecPostStop command (source)
• I'm guessing a part of the issue is relying on the PID being in a subdirectory of /run/. Let's avoid that.

PR Status

• [x] Code finished and ready to be reviewed/tested
• [ ] The fix/enhancement were manually tested (if applicable)

Automatic tests

Automatic tests can be triggered on https://ci-apps-dev.yunohost.org/ after creating the PR, by commenting "!testme", "!gogogadgetoci" or "By the power of systemd, I invoke The Great App CI to test this Pull Request!". (N.B. : for this to work you need to be a member of the Yunohost-Apps organization)

[alexAubin]

Btw several people reported recently that the service failed to start with the systemd log displaying:

Main process exited, code=killed, status=31/SYS

Which apparently is due to a bad system call :

https://unix.stackexchange.com/questions/678494/troubleshoot-a-systemd-service-crash-because-of-systemcallfilter/681075#681075

So we should consider removing or tweaking :

SystemCallFilter=~@clock @debug @module @mount @obsolete @reboot @swap

from the systemd conf

[Josue-T]

!testme

[yunohost-bot]

:stuck_out_tongue_winking_eye:

[Josue-T]

Btw several people reported recently that the service failed to start with the systemd log displaying:

Main process exited, code=killed, status=31/SYS

Which apparently is due to a bad system call :

https://unix.stackexchange.com/questions/678494/troubleshoot-a-systemd-service-crash-because-of-systemcallfilter/681075#681075

So we should consider removing or tweaking :

SystemCallFilter=~@clock @debug @module @mount @obsolete @reboot @swap

from the systemd conf

This sould be already fixed by #330

[tituspijean]

@Josue-T users reported in the forum and the chatrooms that the "fix" proposed in this PR is not working. 🤔

Same permission error on the new PIDFile location.

[Josue-T]

Well, now i understand. It's an issue on bullseye. On buster we don't have this issue. I'll do some test and find a fix.

[Josue-T]

335 should fix the issue.