cinder backup reset status

https://specs.openstack.org/openstack/cinder-specs/specs/juno/
support-reset-state-for-backup.html

Added a testcase for backup reset status to error state.

- Added an api for backup_reset_status
- Added a testcase for status change from available to error.

Change-Id: Ieb5bffddc1e91bfb5fc13d53f16fcdf611876a07
2 files changed