Switch the base URL to git.openstack.org

The git repositories on github for openstack are mirrors of the primary
repositories, which are hosted on git.openstack.org, so switch as much
as I can to using the primary, rather than the github mirror.

Change-Id: Idcfda49a691582055256b830c61e098f4a271339
diff --git a/README.md b/README.md
index 93d1396..b2603e7 100644
--- a/README.md
+++ b/README.md
@@ -30,7 +30,7 @@
 `stackrc` for the default set).  Usually just before a release there will be
 milestone-proposed branches that need to be tested::
 
-    GLANCE_REPO=https://github.com/openstack/glance.git
+    GLANCE_REPO=git://git.openstack.org/openstack/glance.git
     GLANCE_BRANCH=milestone-proposed
 
 # Start A Dev Cloud