Stop showing image locations

This is generally considered insecure because it may reveal
sensitive data [1].
Furthermore, it happens that the default Ceph perms cause fatal
ERRORs with this setting:
1) when Glance wants to remove an image, it cannot list children
because Cinder or Nova might have created a linked volume clone
behind the scenes and it is put in another pool (volumes/vms)
which Glance cannot normally access;
2) when Nova wants to create an image, it lacks permissions
to write to the images pool.

Thus, I propose that Kolla Ansible stops setting this by default
and relies on the working defaults.
The downside is that this disables optimisations in Cinder and Nova.
On the other hand, these optimisations have nasty behaviour of
being linked directly to the original image, preventing its removal.

[1] https://docs.openstack.org/glance/yoga/configuration/glance_api.html#DEFAULT.show_multiple_locations

Change-Id: I63ee9a6eefd8593f2169bba34dbb699f413d7cf8
Depends-On: https://review.opendev.org/c/openstack/kolla-ansible/+/860093
Depends-On: https://review.opendev.org/c/openstack/kolla-ansible/+/860291
Closes-Bug: #1992153