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/tools/build_tempest.sh b/tools/build_tempest.sh
index 1758e7d..6c527f5 100755
--- a/tools/build_tempest.sh
+++ b/tools/build_tempest.sh
@@ -2,7 +2,7 @@
 #
 # **build_tempest.sh**
 
-# Checkout and prepare a Tempest repo: https://github.com/openstack/tempest.git
+# Checkout and prepare a Tempest repo: git://git.openstack.org/openstack/tempest.git
 
 function usage {
     echo "$0 - Check out and prepare a Tempest repo"