pthread/tst-cancel28: Fix barrier re-init race condition

When running this test on the OpenRISC port I am working on this test
fails with a timeout.  The test passes when being straced or debugged.
Looking at the code there seems to be a race condition in that:

  1 main thread: calls xpthread_cancel
  2 sub thread : receives cancel signal
  3 sub thread : cleanup routine waits on barrier
  4 main thread: re-inits barrier
  5 main thread: waits on barrier

After getting to 5 the main thread and sub thread wait forever as the 2
barriers are no longer the same.

Removing the barrier re-init seems to fix this issue.  Also, the barrier
does not need to be reinitialized as that is done by default.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
(cherry picked from commit 9874ca536b)

sysdeps/pthread/tst-cancel28.c

@@ -69,7 +69,6 @@ do_test (void)
 
   xpthread_cancel (timer_thread);
 
-  xpthread_barrier_init (&barrier, NULL, 2);
   xpthread_barrier_wait (&barrier);
 
   return 0;