LXC: fix memory leak in virLXCControllerSetupDevPTS

We forgot to free the mount_options.
Signed-off-by: NGao feng <gaofeng@cn.fujitsu.com>

src/lxc/lxc_controller.c

@@ -1353,6 +1353,7 @@ virLXCControllerSetupDevPTS(virLXCControllerPtr ctrl)
 cleanup:
     VIR_FREE(opts);
     VIR_FREE(devpts);
+    VIR_FREE(mount_options);
     return ret;
 }