Match ns_server assigned ports to projector

ns_server assigns ports to projector decrementing by 1
indexer should follow same logic

Change-Id: I9deaff798bed8f88a4e04d2a0eb04935c954f34f
Reviewed-on: http://review.couchbase.org/43679
Reviewed-by: Sarath Lakshman <sarath@couchbase.com>
Tested-by: Sarath Lakshman <sarath@couchbase.com>