CBQE-0 add wait time after rebalance out
the last CE node in cluster

Change-Id: Id18f4706ffc079db81299eb10a9aa5df8e82542d
Reviewed-on: http://review.couchbase.org/40504
Reviewed-by: Thuan Nguyen <soccon@gmail.com>
Tested-by: Thuan Nguyen <soccon@gmail.com>