Update repo namespace search list
Update repo namespace search list

With the new namespaces we have to look around a bit more to find
repos top copy into the DevStack working directory. Add:

* starlingx/
* x/
* zuul/

Depends-On: https://review.opendev.org/653988
Change-Id: I8a55522a5fee46f415f0c0ce580ded3476133460
Signed-off-by: Dean Troyer <8b9d4b97f386f6f54679ab5c0c082ebdb224d70a@gmail.com>

dtroyer/devstack,nawawi/openstack,nawawi/openstack,openstack-dev/devstack,dtroyer/devstack,openstack-dev/devstack