Revert "nwfilter: Move save of config until after successful assign"

This reverts commit b3e71a8830.

As it turns out this ends up very badly as the @def could be Free'd
even though it's owned by @obj as a result of the AssignDef.

src/conf/virnwfilterobj.c

@@ -524,14 +524,14 @@ virNWFilterObjListLoadConfig(virNWFilterObjListPtr nwfilters,
         goto error;
     }
 
-    if (!(obj = virNWFilterObjListAssignDef(nwfilters, def)))
-        goto error;
-
     /* We generated a UUID, make it permanent by saving the config to disk */
     if (!def->uuid_specified &&
         virNWFilterSaveConfig(configDir, def) < 0)
         goto error;
 
+    if (!(obj = virNWFilterObjListAssignDef(nwfilters, def)))
+        goto error;
+
     VIR_FREE(configFile);
     return obj;