support zte vstorage driver for Cinder

This blueprint is to add Cinder driver for ZTE Vstorage iSCSI arrays.

support volume driver set readonly for Cinder

Currently, cinder has a interface set volume readonly. It just set volume metadata readonly as True. When the volume attach a instance, the libvirt can control the readonly. But if the user attach the volume to a host manually, the volume readonly cann't be controled. So, the cinder can set the readonly prope...