Revert "nm-policy: stop rechecking autoactivation if device is unregistered"

When we register the auto-activate, the device has to be registered in
NMPolicy, the assertion is correct and ensure that.

This reverts commit 712729f652.

src/core/nm-policy.c

@@ -1662,15 +1662,14 @@ nm_policy_device_recheck_auto_activate_schedule(NMPolicy *self, NMDevice *device
 
     g_return_if_fail(NM_IS_POLICY(self));
     g_return_if_fail(NM_IS_DEVICE(device));
-    if (g_signal_handler_find(device,
+    nm_assert(g_signal_handler_find(device,
                                     G_SIGNAL_MATCH_DATA,
                                     0,
                                     0,
                                     NULL,
                                     NULL,
                                     NM_POLICY_GET_PRIVATE(self))
-        == 0)
-        return;
+              != 0);
 
     if (!c_list_is_empty(&device->policy_auto_activate_lst)) {
         /* already queued. Return. */