MB-100: fix TypeError: wait_node_restarted() got multiple values

Change-Id: Ib5bf51d3e39aa3218537468fd451d9cd9cf12a03
Reviewed-on: http://review.couchbase.org/24958
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: Andrei Baranouski <andrei.baranouski@gmail.com>