Fix GitHub tarball URL for monasca-thresh
Fix GitHub tarball URL for monasca-thresh

And the options docs, they were misleading.

Change-Id: Ie388938fc207c982c5650221baee354a5bb9be30
Co-Authored-By: Radosław Piliszek <8759e5988b55949fdf66960d1c0fc9651a951f3b@gmail.com>

openstack/kolla,openstack/kolla