MB-7730 Master event for forced view compaction during rebalance.

Change-Id: Ibcfc920204cf0eece902fb7df0266a232c18c982
Reviewed-on: http://review.couchbase.org/24572
Reviewed-by: Junyi Xie <junyi.couchbase@gmail.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>