Merge pull request #3610 from matrix-org/rav/fix_looping_calls

changelog.d/3610.feature

synapse/app/homeserver.py

synapse/groups/attestations.py

synapse/handlers/profile.py

synapse/metrics/background_process_metrics.py

synapse/rest/media/v1/media_repository.py

synapse/rest/media/v1/preview_url_resource.py

synapse/storage/client_ips.py

synapse/storage/devices.py

synapse/storage/event_federation.py

synapse/storage/event_push_actions.py

synapse/storage/transactions.py

synapse/util/caches/expiringcache.py