adding test config hercules_4x4 for xdcr runs
adding test config hercules_4x4 for xdcr runs

Change-Id: I4361c5b1bc71980bce139ae2c7c76fa43e22048a
Reviewed-on: http://review.couchbase.org/c/perfrunner/+/138797
Tested-by: Build Bot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: <7c5437523872fffef04ef9d4aaffcc0ca27fba16@gmail.com>

couchbase/perfrunner,couchbase/perfrunner,couchbase/perfrunner,couchbase/perfrunner,couchbase/perfrunner,couchbase/perfrunner