Make geocouch's dialyzer happy

geocouch uses some of the couchdb functions, hence some type specs
need to be adapted in order to make the dialyzer run on geocouch
happy.

Change-Id: Iaea98815ac8670d7222c181f6d11d406ff5295a9
Reviewed-on: http://review.couchbase.org/41951
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Sarath Lakshman <sarath@couchbase.com>