conf: snapshot: Remove file format check from parser

We already have a way stricter check in the code which is doing the
snapshot so duplicating it in the parser does not make much sense. Also
gets rid of an ugly ternary operator.
Signed-off-by: NPeter Krempa <pkrempa@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

src/conf/snapshot_conf.c

@@ -159,17 +159,11 @@ virDomainSnapshotDiskDefParseXML(xmlNodePtr node,
         virDomainDiskSourceParse(cur, ctxt, def->src, flags, xmlopt) < 0)
         goto cleanup;
 
-    if ((driver = virXPathString("string(./driver/@type)", ctxt))) {
-        def->src->format = virStorageFileFormatTypeFromString(driver);
-        if (def->src->format < VIR_STORAGE_FILE_BACKING) {
+    if ((driver = virXPathString("string(./driver/@type)", ctxt)) &&
+        (def->src->format = virStorageFileFormatTypeFromString(driver)) <= 0) {
             virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
-                           def->src->format <= 0
-                           ? _("unknown disk snapshot driver '%s'")
-                           : _("disk format '%s' lacks backing file "
-                               "support"),
-                           driver);
+                           _("unknown disk snapshot driver '%s'"), driver);
             goto cleanup;
-        }
     }
 
     /* validate that the passed path is absolute */