Resolve race condition.

Don't wait for convergence of the ring, because bucket properties are no
longer stored in the ring; instead, wait until the property changes,
which means the gossip has stabilized.

Resolves the race condition in repl_bucket_types for the 2.0.2 release.
Ugh. Can this be simplified to `[] == rpc:call(Node, riak_repl2_rtq, dumpq, [])`?