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=

As of docker-jitsi-meet stable-6433 [1], `/config/interface_config.js`
is regenerated on every boot. The correct way to modify the interface
config is now via `/config/custom-interface_config.js`, which is
appended to a default copy of `interface_config.js` by
`/etc/cont-init.d/10-config` on every boot of the docker image.

Given that `interface_config.js` is considered deprecated by upstream
(all options will eventually be moved to `config.js`), we also deprecate
the `matrix_jitsi_web_interface_config_*` variables in favour of
`matrix_jitsi_web_custom_interface_config_extension`.

[1] https://github.com/jitsi/docker-jitsi-meet/blob/stable-6433/CHANGELOG.md#stable-6433

The domain is invalid with space, so it shouldn't be here

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/1464

The check was checking for an empty string in `matrix_jitsi_prosody_auth_internal_accounts`,
which is unlikely to happen. We should check for an empty list instead.

The check was not validating username/password values, so telling the user that they need a non-empty
username/password is misleading. It was merely checking if there's at least one entry in the list.

This patch adjusts the check and message accordingly.

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.

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/1377

Regresion since https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/1139

I changed the conditional statement in prosody systemd template to bind the localhost port by default if people have set ```matrix_nginx_proxy_enabled == false ```.
Hopefully that should make it the default behaviour now.

Added:
 - Conditional localhost Port bindings for Jitsi Prosody systemd template
- Added variable to main.yml to allow overriding from vars.yml