Fix PI mutex check in pthread_cond_broadcast and pthread_cond_signal

Fix PI mutex check in pthread_cond_broadcast and pthread_cond_signal

Fixes BZ #15996.

The check had a typo - it checked for PTHREAD_MUTEX_ROBUST_NP instead
of PTHREAD_MUTEX_ROBUST_NORMAL_NP.  It has now been replaced by the
already existing convenience macro USE_REQUEUE_PI.

(cherry picked from commit 2770d15e7e880821fc586619c59eb45180628e16)