
When using the "openstack image cache clear" command, the "clear_cache" method from the OpenStack SDK is used. It expects its only argument to be one of "both", "cache" or "queue". However, when passing neither "--cache" nor "--queue", it is currently passed None as a value. Fix this by specifying "both" as the default value to be passed. Change-Id: I17c6e3d435a84b4ba453845086ff3fe272b54f58