Replace GdmUser with AccountsService

The GdmUser copy+paste code has been superseded by AccountsService,
so kill the former and use the latter.

https://bugzilla.gnome.org/show_bug.cgi?id=650893

src/main.c

@@ -534,7 +534,7 @@ main (int argc, char **argv)
   /* Disable debug spew from various libraries */
   g_log_set_handler ("Gvc", G_LOG_LEVEL_DEBUG,
                      muted_log_handler, NULL);
-  g_log_set_handler ("GdmUser", G_LOG_LEVEL_DEBUG,
+  g_log_set_handler ("AccountsService", G_LOG_LEVEL_DEBUG,
                      muted_log_handler, NULL);
   g_log_set_handler ("Bluetooth", G_LOG_LEVEL_DEBUG | G_LOG_LEVEL_MESSAGE,
                      muted_log_handler, NULL);