glx: check for indirect context in CreateContextAttribsARB()

Commit 99f0365b "Add a command line argument for disabling indirect GLX"
added a test to check if indirect context are enabled in
`DoCreateContext()` but `__glXDisp_CreateContextAttribsARB()` doesn't
use `DoCreateContext()` and doesn't check if indirect context is
enabled.

As a result, clients can still manage to create indirect contexts using
`glXCreateContextAttribsARB()` even if indirect contexts are disabled,
which can possibly crash Xservers such as Xwayland or Xephyr when the
context is destroyed.

To avoid the issue, check for `enableIndirectGLX` in
`__glXDisp_CreateContextAttribsARB()` as well.

Fixes: 99f0365b "Add a command line argument for disabling indirect GLX"
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107508


Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
(cherry picked from commit 75448671)