testpostupgrade: Handle missing manila properly
testpostupgrade: Handle missing manila properly

If Manila VM was not found, it's (empty) name was still used in subsequent
commands causing false positives in logs.

aspiers/automation,aspiers/automation,gosipyan/automation,SUSE-Cloud/automation,gosipyan/automation,gosipyan/automation,SUSE-Cloud/automation,aspiers/automation,aspiers/automation,gosipyan/automation,SUSE-Cloud/automation,SUSE-Cloud/automation