present: Check the whole exec queue on event

Later events are sometimes added in front of the queue (e.g.
if page flipping fails) so we need to check the whole queue
on event.

Signed-off-by: Louis-Francis Ratté-Boulianne <lfrb@collabora.com>
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
(cherry picked from commit c2f2b25a)