PR/47703: Yasushi Oshima: pthread_cond_timedwait() does not wait
after call pthread_condattr_setclock(CLOCK_MONOTONIC)

_lwp_park(2) expects a realtime clock, and it gets passed a monotonic
one.  Since monotonic < real, it never sleeps. This patch adjusts
the monotonic clock to be a real one before it passes is to
_lwp_park(2). This is the minimal hacky fix and it will be fixed
properly in _lwp_park(2) in the future.

XXX: pullup to 6.

(christos)