Topology on raft is still an experimental feature. The RPC verbs
introduced in that mode shouldn't be used when it's disabled, otherwise
we lose the right to make breaking changes to those verbs.
First, make sure that the aforementioned verbs are not sent outside the
mode. It turns out that `raft_pull_topology_snapshot` could be sent
outside topology-on-raft mode - after the PR, it no longer can.
Second, topology-on-raft mode verbs are now not registered at all on the
receiving side when the mode is disabled.
Additionally tested by running `topology/` tests with
`consistent_cluster_management: True` but with experimental features
disabled.
Fixes: scylladb/scylladb#15862Closesscylladb/scylladb#15917
* github.com:scylladb/scylladb:
storage_service: fix indentation
raft: topology: only register verbs in topology-on-raft mode
raft: topology: only pull topology snapshot in topology-on-raft mode
5cf18b18b2