`always` is an nginx suffix, which shouldn't have been added to these.

This may proof useful to someone in the future.

We've had it on `matrix-nginx-proxy` before, but
our initial support for Traefik did not include any of these security
headers.

Previously, we had to run it at a subpath, like `/synapse-admin`.

We can now dedicate a whole domain and the `/` path to it, should we
wish to do so.

Previously, it had to go through matrix-nginx-proxy.
It's exposed to Traefik directly via container labels now

Previously, it had to go through matrix-nginx-proxy.
It's exposed to Traefik directly via container labels now.

Related to 6a31fba346d9da434, 6a31fba346.

Related to https://github.com/Awesome-Technologies/synapse-admin/issues/322

Fixup for 6a31fba346

Related to f165aa5d48

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2424

- forego removing Docker images - it's not effective anyway, because it
  only removes the last version.. which is a drop in the bucket, usually

- do not reload systemd - it's none of our business. `--tags=start`,
  etc., handle this

- combine all uninstall tasks under a single block, which only runs if
  we detect traces (a leftover systemd .service file) of the component.
  If no such .service is detected, we skip them all. This may lead to
  incorect cleanup in rare cases, but is good enough for the most part.

These `init.yml` (now `inject_into_nginx_proxy.yml`) tasks do not need
to `always` run. They only need to run for `setup-all` and
`setup-nginx-proxy`. Unless we're dealing with these 2 tags, we can
spare ourselves a lot of work.

This patch also moves the `when` statement from `init.yml` into
`main.yml` in an effort to further optimize things by potentially
avoiding the extra file include.

This paves the way for installing other roles into `roles/galaxy` using `ansible-galaxy`,
similar to how it's done in:

- https://github.com/spantaleev/gitea-docker-ansible-deploy
- https://github.com/spantaleev/nextcloud-docker-ansible-deploy

In the near future, we'll be removing a lot of the shared role code from here
and using upstream roles for it. Some of the core `matrix-*` roles have
already been extracted out into other reusable roles:

- https://github.com/devture/com.devture.ansible.role.postgres
- https://github.com/devture/com.devture.ansible.role.systemd_docker_base
- https://github.com/devture/com.devture.ansible.role.timesync
- https://github.com/devture/com.devture.ansible.role.vars_preserver
- https://github.com/devture/com.devture.ansible.role.playbook_runtime_messages
- https://github.com/devture/com.devture.ansible.role.playbook_help

We just need to migrate to those.