Enable "cinder delete" can delete multiple volumes in one request

"nova delete" can delete multiple servers in one request but
"cinder delete" can only delete one volume in one request, it is
better to enhance cinder client to support remove multiple volumes
in one request.

Change-Id: I6a63aa3d7e4c152ae5e45bf2b36d862bdcd6df33
Closes-Bug: #1241941