dix: Remove clients from input and output ready queues after closing

Delay removing the client from these two queues until all potential
I/O has completed in case we mark the client as ready for reading or
with pending output during the close operation.

Bugzilla: https://bugs.freedesktop.org/100957


Signed-off-by: Keith Packard <keithp@keithp.com>
Tested-by: Nick Sarnie <commendsarnex@gmail.com>
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
(cherry picked from commit d9e23ea4)