Upgrade tests: minor tempest failures

Some not-so-important tempest test cases occasionally fail in the charm-upgrade and openstack-upgrade tests and have been thus temporarily blocklisted. 

To reproduce, remove the [blocklist](https://github.com/openstack-charmers/charmed-openstack-tester/blob/master/tests/charm-upgrade/tests/tests.yaml) and run

```
tox -e charm-upgrade-focal-ussuri
```