sip: origin: Destroy registration handle on deinit

Otherwise shutting down may be timing out, because there are pending messages.
Calling nua_destroy_handle() will kill any dialog/leg.

plugins/sip/calls-sip-origin.c

@@ -1037,6 +1037,8 @@ deinit_sip_account (CallsSipOrigin *self)
   remove_calls (self, NULL);
 
   if (self->nua) {
+    g_debug ("Clearing any handles");
+    g_clear_pointer (&self->oper->register_handle, nua_handle_destroy);
     g_debug ("Requesting nua_shutdown ()");
     self->is_nua_shutdown = FALSE;
     self->is_shutdown_success = FALSE;