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

Change-Id: Ibb53211f6afd0ad603af8d9ada06adfcaea2c77c
Reviewed-on: http://review.couchbase.org/34697
Reviewed-by: Philip Labee <philip@couchbase.com>
Tested-by: Philip Labee <philip@couchbase.com>