CBLT-202:  set default value of BLD_TO_RELEASE in upload_cblite_android_artifacts jobs

Change-Id: I75753b0a2f2527c231871b8d4e3126227515e012
Reviewed-on: http://review.couchbase.org/34696
Reviewed-by: Philip Labee <philip@couchbase.com>
Tested-by: Philip Labee <philip@couchbase.com>