Automatically integate matrix-media-repo with Valkey (if enabled) (#4851)

* This push request is about handling Traefik ipallowlist to synapse-admin application.

It's my first push request. If I forgot something please let me know. :-)

* Changed position of variable and naming for better expandebility of traefik options

* Remove useless `noqa var-naming` comment and too many blank lines at the end of the file

* If redis ist enabled for matrix media repo it failes to connect to valkey due to inproper configuration.

* Updated solution for fixing MMR redis connection

* Clean up

* Update valkey_container_network condition

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Co-authored-by: AkDk7 <joerg@pannbacker.email>
Co-authored-by: Slavi Pantaleev <slavi@devture.com>

roles/custom/matrix-media-repo/defaults/main.yml

@@ -895,13 +895,7 @@ matrix_media_repo_redis_database_number: 0
 
 # The Redis shards that should be used by the media repo in the ring. The names of the
 # shards are for your reference and have no bearing on the connection, but must be unique.
-matrix_media_repo_redis_shards:
-  - name: "server1"
-    addr: ":7000"
-  - name: "server2"
-    addr: ":7001"
-  - name: "server3"
-    addr: ":7002"
+matrix_media_repo_redis_shards: []
 
 # Optional sentry (https://sentry.io/) configuration for the media repo