Revert "logical: Only raw volumes are supported"

This reverts commit 6682d621.

The "if (vol->target.format != VIR_STORAGE_FILE_RAW)" check in the
createVol backend. This check is bogus because virStorageVolDefParseXML()
in conf/storage_conf.c sets target.format only if volOptions in
virStoragePoolTypeInfo has formatFromString set, and that's not the
case the logical backend.

So the check always fails and breaks volume creation.

src/storage/storage_backend_logical.c

@@ -912,12 +912,6 @@ virStorageBackendLogicalCreateVol(virConnectPtr conn,
     struct stat sb;
     bool created = false;
 
-    if (vol->target.format != VIR_STORAGE_FILE_RAW) {
-        virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
-                       _("only RAW volumes are supported by this storage pool"));
-        return -1;
-    }
-
     if (vol->target.encryption != NULL) {
         virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
                        "%s", _("storage pool does not support encrypted "