[libvirt] [PATCH] Don't squash file format on volume refresh

A while back, code was added to storage_backend.c:virStorageBackendUpdateVolTargetInfoFD to try to determine the volume format for iscsi volumes. Unfortunately this function is also called for refreshing file volumes, which has the effect of setting the format as 'raw' whenever a volume is refreshed (ex. after calling virsh vol-info). The attached patch moves the offending code into a wrapper function in the scsi driver. I haven't played with the scsi support yet so this is untested though it's largely code movement. Thanks, Cole