r/bitwarden_rs: Remove dangling container at start

If the *vaultwarden* service terminates unexpectedly, e.g. due to a
power loss, `podman` may not successfully remove the container.  We
therefore need to try to delete it before starting it again, or `podman`
will exit with an error because the container already exists.

roles/bitwarden_rs/templates/vaultwarden.service.j2

@@ -4,6 +4,7 @@ Description=Vaultwarden API server
 [Service]
 Type=notify
 NotifyAccess=all
+ExecStartPre=-/usr/bin/podman container rm --force --ignore vaultwarden
 ExecStart=/usr/bin/podman run \
     --pull never \
     --sdnotify=conmon --cgroups=no-conmon \