Description of problem:
`tempest cleanup` command is not cleaning up the region(s) tempest has creates during its execution.

Running  `tempest run --smoke` (even followed by `tempest cleanup`) a few times, will results in many unused regions being created and left behind.

Version-Release number of selected component (if applicable):
13.0.7
13.0.8
(Haven't tested version lower than 13.0.7)

How reproducible:

$ openstack region list
+-----------+---------------+-------------+
| Region    | Parent Region | Description |
+-----------+---------------+-------------+
| regionOne | None          |             |
+-----------+---------------+-------------+
$ tempest cleanup --init-saved-state
$ ll saved_state.json 
-rw-rw-r--. 1 stack stack 107598 Oct 18 02:32 saved_state.json <=== state is saved 
$ tempest run --smoke
$ tempest cleanup --dry-run
Begin cleanup
Process 0 projects
$ cat dry_run.json 
{
  "_projects_to_clean": {},
  "domains": [],
  "flavors": [],
  "images": [],
  "projects": [],
  "roles": [],
  "users": []
}
$ openstack region list
+---------------------------+---------------+-------------+
| Region                    | Parent Region | Description |
+---------------------------+---------------+-------------+
| regionOne                 | None          |             |
| tempest-region-1060190437 | None          |             | <=====
| tempest-region-259179736  | None          |             | <===== regions are left behind, after cleaning up (--dry-run): this is expected
| tempest-region-303446827  | None          |             | <=====
| tempest-region-945563805  | None          |             | <=====
+---------------------------+---------------+-------------+
$ tempest cleanup
Begin cleanup
Process 0 projects
$ openstack region list
+---------------------------+---------------+-------------+
| Region                    | Parent Region | Description |
+---------------------------+---------------+-------------+
| regionOne                 | None          |             |
| tempest-region-1060190437 | None          |             | <=====
| tempest-region-259179736  | None          |             | <=====  regions are left behind, after cleaning up: this is not expected
| tempest-region-303446827  | None          |             | <=====
| tempest-region-945563805  | None          |             | <=====
+---------------------------+---------------+-------------+

Actual results:

`tempest cleanup` should restore the environment to the same state where it was before running `tempest run`.

Expected results:
`tempest cleanup` leaves behind regions it created during its execution