Comment 3 for bug 1792400

To avoid unintended processes to be acted on we should combine that with exec.
Man page:
-p, --pidfile pid-file
Check whether a process has created the file pid-file. Note: using this matching option alone might cause unintended processes to be acted on, if the old process terminated without being able to remove the pid-file.

Text would be like:
Let daemon start/stop actions only using --exec use --pidfile as well to avoid affecting or being affected by processed of the same name in containers. Let calls only using pidfile add --exec to avoid acting on processes reusing the PIDs.

There is some detail that I'm not sure it was intended or not and we have to be careful.
- debian/samba.samba-ad-dc.init
- debian/samba.smbd.init
On start they used --exec so they would block if "the other" was running
On stop they used --pidfile (so they only stop their own)
I wondered if that would be an issue, but those two init also share the PIDfile path, so it would not really behave differently after the change.

I opened an MP for review and discussions at [1].
In addition there is a xenial PPA to test from [2].

[1]: https://code.launchpad.net/~paelzer/ubuntu/+source/samba/+git/samba/+merge/355532
[2]: https://launchpad.net/~ci-train-ppa-service/+archive/ubuntu/3435