Add UPSTREAM_CHECK_URI to check the correct latest stable verison.
Before the patch:
$ devtool latest-version libmash
INFO: Current version: 0.9.9.9
INFO: Latest version:
After the patch:
$ devtool latest-version libmash
INFO: Current version: 0.9.9.9
INFO: Latest version: 0.9.9.9
Signed-off-by: Yi Zhao <yi.zhao@windriver.com>