Reverts b1b4ba501fdfaa, 90c9801c560b6, a3c84f78ca9c65a, ..

I haven't really traced it (yet), but on some servers, I'm observing
`ansible-playbook ... --tags=start` completing very slowly, waiting
to stop services. I can't reproduce this on all Matrix servers I manage.
I suspect that either the systemd version is to blame or that some
specific service is not responding well to some `docker kill/rm` command.

`ExecStop` seems to work great in all cases and it's what we've been
using for a very long time, so I'm reverting to that.

ExecStopPost should allow us to clean up (docker kill + docker rm)
even if the ExecStart (docker run ..) command failed, and not just after
a graceful service stop was initiated.

Source: https://www.freedesktop.org/software/systemd/man/systemd.service.html#ExecStopPost=

* Upgrade Mjolnir from 1.1.20 to version 1.2.1

https://hub.docker.com/r/matrixdotorg/mjolnir/tags

using the "latest" tag seems inefficient as it doesn't actually redirect to the latest release

In any case, the latest release is now 1.2.1

docker pull matrixdotorg/mjolnir:v1.2.1

* Fixup

Co-authored-by: Slavi Pantaleev <slavi@devture.com>

Until now, we were leaving services "enabled"
(symlinks in /etc/systemd/system/multi-user.target.wants/).

We clean these up now. Broken symlinks may still exist in older
installations that enabled/disabled services. We're not taking care
to fix these up. It's just a cosmetic defect anyway.

Upgrade mjolnir (v0.1.19 -> v1.1.20)

Remark: interesting version number increase :-)

Signed-off-by: Ahmad Haghighi <haghighi@fedoraproject.org>