A test flake revealed a bug in the CSI unpublish workflow, where an unpublish
that comes from a client that's successfully done the node-unpublish step will
not have the claim checkpointed if the controller-unpublish step fails. This
will result in a delay in releasing the volume claim until the next GC.
This changeset also ensures we're using a new snapshot after each write to raft,
and fixes two timing issues in test where either the volume watcher can
unpublish before the unpublish RPC is sent or we don't wait long enough in
resource-restricted environements like GHA.
