glx: Fix use after free in MakeCurrent

The fix from commit c468d34c - "glx: Set ContextTag for all contexts"
is actually incomplete, it correctly sets the context tag for direct
contexts as well, but would fail to mark the context's currentClient.

As a result, when the context is destroyed, it would be freed
immediately rather than being just scheduled for deletion, even though
it is still current for some client. leading to a use-after-free.

Make sure to also set the context's currentClient for direct contexts as
well, not just indirect ones.

Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
Fixes: c468d34c - "glx: Set ContextTag for all contexts"
Closes: xorg/xserver#1186
Reviewed-by: Adam Jackson <ajax@redhat.com>
5 jobs for issue1186 in 4 minutes and 22 seconds
Status Job ID Name Coverage
  Docker Image
passed debian-buster #11077814

00:00:27

 
  Build And Test
passed autotools #11077815

00:03:55

passed meson #11077816

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passed meson-noglamor #11077817

00:01:48

passed mingw-cross-build #11077818

00:00:48