The register operation was registering user_database which is a global
variable in group_vars/all.yml. This results in glance not being deployable
because user_database is overwrriten at keystone task registration time.
The result of this is the playbooks fail to deploy.
Change-Id: Ic69725fb09aa0a368ec5b0d8f47bfc768c29c70c
Closes-Bug: #1486876