WAL-E doesn't attempt to create swift container if tenant changes

Changing the WAL-E swift configuration to a new container should result in "ensure_swift_container()" firing again to make sure the container exists.

At the moment this is only triggered if the URI changes:
if reactive.helpers.data_changed("postgresql.wal_e.uri", uri):

However, keeping the same URI (e.g. 'swift://postgresql') but pointing at a new swift tenant should also trigger this.

In case we keep the same URI and Tenant but look at a different instance of swift, this should probably trigger on a change of:

* os_auth_url
* os_tenant_name
* wal_e_storage_uri