We don't need to wait before drawing to the fake front buffer, as front
buffer rendering by definition is allowed to produce artifacts.
Fixes hangs in some cases when re-using the fake front buffer, due to it
still being busy (i.e. in use for presentation).
Cc: mesa-stable@lists.freedesktop.org
Bugzilla: https://bugs.freedesktop.org/106404
Bugzilla: https://bugs.freedesktop.org/107757
Tested-by: Olivier Fourdan <ofourdan@redhat.com>
Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com>