Revert "cinder backup force-delete when backup is error"

force-delete feature is backend specific and not implemented by ceph.
It return 405 in case of ceph.
http://logs.openstack.org/01/458201/2/check/gate-tempest-dsvm-full-ceph-plugin-src-glance_store-ubuntu-xenial/d058f29/logs/testr_results.html.gz

Currently it block the glance_store gate where ceph job is voting.
Let's revert this for now and discuss such backend specific feature
should be tested on Tempest side or not.

This reverts commit 31169e21d6f00fb65b8e7bd104860a82a631b69d.

Related-Bug: #1687538
Change-Id: I81c0911812945f8ada7c09fe98690aabacb0eda1
4 files changed