util/queue: fix a data race detected by TSAN when finishing the queue

util/queue: fix a data race detected by TSAN when finishing the queue

Thread sanitizer complains if it detects that the pthread_barrier
is destroyed when a thread might still blocked on the barrier.

Fix this by destroying the barrier only if pthread_barrier_wait
returns PTHREAD_BARRIER_SERIAL_THREAD which is the value for success.

In practice this shouldn't fix anything serious given that this code
is only called when the disk cache is destroyed.

Original patch from Timothy Arceri.

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/4342
Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/13861>