MB-10265 do not include ejected nodes into rebalance progress

Change-Id: I73e28398e9d924ab01bf7eaff39449ca2a3972ce
Reviewed-on: http://review.couchbase.org/35112
Tested-by: Artem Stemkovski <artem@couchbase.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>