Fixes test_volume_backup_delete failing during tearDown.

This test is currently failing because after doing
self.backups_client.delete_backup(), the backup
goes into deleting status, and directly afterward tearDown
is called, during which the
test_utils.call_and_ignore_notfound_exc calls the
backup deletion method again... However, the backup
is still in deleting status, as it has not been fully
deleted, causing a 400 Bad Request to be thrown.

This patch adds a waiter (wait_for_resource_deletion)
call right after the first delete backup call is made.

Change-Id: Ie3e8e7371bb169043377bfd4e04c1320f8939004
Partial-Bug: #1670553
1 file changed