CBQE-927: test online_upgrade_rebalance_in_with_ops

reproducer MB-7571,MB-7771

Change-Id: I198f3e8f6ebcc7e70c4ca231a9611157f8077bb8
Reviewed-on: http://review.couchbase.org/24787
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: Andrei Baranouski <andrei.baranouski@gmail.com>