Fix use-after-free crash in media playback and use French tones

Replace North American ringback/busy tones with French standard
(440 Hz single tone with 1.5s/3.5s and 0.5s/0.5s cadences).

Fix a crash in on_playing_done where the error/cancel path freed
the MediaPlaybackData via g_autoptr without clearing the owning
pointer (data_calling/data_busy), leaving a dangling pointer that
would segfault on the next stop call.

src/calls-media-playback.c

@@ -175,6 +175,18 @@ on_playing_done (GObject      *object,
       g_warning ("Playing '%s' failed: %s",
                  playback_event_to_string (data->event),
                  error->message);
+
+    switch (data->event) {
+    case PLAYBACK_CALLING:
+      data->self->data_calling = NULL;
+      break;
+    case PLAYBACK_BUSY:
+      data->self->data_busy = NULL;
+      break;
+    case PLAYBACK_LAST:
+    default:
+      break;
+    }
   } else {
     if (g_timer_elapsed (data->timer, NULL) < data->min_playback_time) {
       playback_data (g_steal_pointer (&data));