CBD-1239:  when you change the builder in the master.cfg, change the mapping here

Change-Id: Iefeaef743ba19e650572c03ccc3fbe693ed2e35e
Reviewed-on: http://review.couchbase.org/34479
Reviewed-by: Philip Labee <philip@couchbase.com>
Tested-by: Philip Labee <philip@couchbase.com>