CBD-1425:  cd to correct dir to find CHANGES.out

Change-Id: I0e43f98947cdb4b28575bf39eff625100089162b
Reviewed-on: http://review.couchbase.org/40594
Reviewed-by: Philip Labee <philip@couchbase.com>
Tested-by: Philip Labee <philip@couchbase.com>