CBQE-0 add offline dcp rebalance monitor
if doing upgrade from version 2.x.x to 3.x.x

Change-Id: Ic5e58042da46ebd3a6a657f5d9a8cb6dc8fbc439
Reviewed-on: http://review.couchbase.org/41400
Reviewed-by: Thuan Nguyen <soccon@gmail.com>
Tested-by: Thuan Nguyen <soccon@gmail.com>