Revert "Fix cleanup for volume backup tests"

This reverts commit 2c2484ca6e1835105b4e322a65f6e7f588736e61.

Reason for revert: This change causes failures in RBD backup tests where a container is not expected but being passed by this change.

See failures at
http://storage.gra.cloud.ovh.net/v1/AUTH_dcaab5e32b234d56b626f72581e3644c/zuul_opendev_logs_56f/889826/1/check/cinder-plugin-ceph-tempest/56f21fd/testr_results.html

Change-Id: I98a75cbf119ba8126253a681c046f4cf44b1607e
8 files changed