Revert "dri2: Don't make reference to noClientException"

It's true that the value would always be -1, if it's not zero, but it's
usually zero is the problem. As a result we return failure from
otherwise successful indirect GLX paths, which isn't very nice of us.

This reverts commit 7d33ab0f.

Fixes: xorg/xserver#211
3 jobs for revert-noclientexception-thinko in 5 minutes and 23 seconds
Status Job ID Name Coverage
  Docker Image
passed #1484504
debian-testing

00:00:59

 
  Build And Test
passed #1484505
autotools-build-and-test

00:04:23

passed #1484506
meson-build-and-test

00:02:33