Backported from X.org:

 commit 7762a602c1dfdd8cfcf2b8c2281cf4d683d05216
 Author: Keith Packard <keithp@keithp.com>
 Date:   Thu May 19 15:05:55 2016 -0700

    dix/os: Merge priority computation into SmartScheduleClient

    Instead of having scheduling done in two places (one in
    WaitForSomething, and the other in SmartScheduleClient), just stick
    all of the scheduling in SmartScheduleClient.
Signed-off-by: Keith Packard <keithp@keithp.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Backported-to-NX-by: Mike Gabriel <mike.gabriel@das-netzwerkteam.de>