MB-7525 Reset replica index utilization stats as well

When receive an utilization stats reset request, don't
forget to reset them in the replica index as well.

Change-Id: Ib1d5d671f786745478dca4f341882f33a73d1d5e
Reviewed-on: http://review.couchbase.org/24015
Tested-by: Filipe David Borba Manana <fdmanana@gmail.com>
Reviewed-by: Volker Mische <volker.mische@gmail.com>