netdev-linux: Quiet down ingress policing.

If we attempt to remove ingress policing and receive "invalid
argument" it means that policing isn't compiled into the kernel.
If it isn't compiled in then accept that policing has been
successfully removed.

lib/netdev-linux.c

@@ -1163,7 +1163,7 @@ netdev_linux_remove_policing(struct netdev *netdev)
     error = nl_sock_transact(rtnl_sock, &request, &reply);
     ofpbuf_uninit(&request);
     ofpbuf_delete(reply);
-    if (error && error != ENOENT) {
+    if (error && error != ENOENT && error != EINVAL) {
         VLOG_WARN_RL(&rl, "%s: removing policing failed: %s",
                      netdev_name, strerror(error));
         return error;