MB-11610:  rel-3.0.0.xml uses branch "3.0.0" for couchdbx-app

Change-Id: I191451ad52c50cab22e4f26377e6e5c5982e236c
Reviewed-on: http://review.couchbase.org/39056
Reviewed-by: Philip Labee <philip@couchbase.com>
Tested-by: Philip Labee <philip@couchbase.com>