Since the cluster name might be used for various purposes on nodes, we
should let all nodes "know" about a cluster rename by running the post
hook on all nodes. This will make cluster rename slightly
slower/costlier, but it is not/shouldn't be an operation that is run
very often.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Olivier Tharan <olive@google.com>