CBD-1425:  cd to correct dir to find ZIP file to upload

Change-Id: Id8d874ff5343eec6060f398a0a8517cc87330d96
Reviewed-on: http://review.couchbase.org/40592
Reviewed-by: Philip Labee <philip@couchbase.com>
Tested-by: Philip Labee <philip@couchbase.com>