While "cinder snapshot-delete" and "cinder delete" allow multiple resources to be deleted in a single command, "cinder backup-delete" request can only delete one backup at a time. Adding this capability to backups in cinderclient. Enables "cinder backup-delete" to delete multiple backups in a single command.
With this change the command can be run as below:
cinder backup-delete <backup> [<backup>...]
DocImpact
Closes-Bug: #1543056
Implements: blueprint cli-backup-multiple-deletes
Change-Id: I767710bda3b7c358c6525c9a9f074010084e411d