Add couch_upr to dialyzer

Change-Id: Icf33e57b982b4cfc6437eedb8e616e1b0ed3f0c7
Reviewed-on: http://review.couchbase.org/35241
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Filipe David Borba Manana <fdmanana@gmail.com>