Don't refuse to start worker if media listener configured. (#7002)

Instead lets just warn if the worker has a media listener configured but
has the media repository disabled.

Previously non media repository workers would just ignore the media
listener.

changelog.d/7002.misc

@@ -0,0 +1 @@
+Merge worker apps together.

synapse/app/generic_worker.py

@@ -494,6 +494,7 @@ class GenericWorkerServer(HomeServer):
                 elif name == "federation":
                     resources.update({FEDERATION_PREFIX: TransportLayerServer(self)})
                 elif name == "media":
+                    if self.config.can_load_media_repo:
                         media_repo = self.get_media_repository_resource()
 
                         # We need to serve the admin servlets for media on the
@@ -508,6 +509,11 @@ class GenericWorkerServer(HomeServer):
                                 "/_synapse/admin": admin_resource,
                             }
                         )
+                    else:
+                        logger.warning(
+                            "A 'media' listener is configured but the media"
+                            " repository is disabled. Ignoring."
+                        )
 
                 if name == "openid" and "federation" not in res["names"]:
                     # Only load the openid resource separately if federation resource