Detect premature ETIMEDOUT events and mitigate the issue.

There is a circumstance where the NaCl environment will return immediately from
pthread_cond_timedwait() with an ETIMEDOUT, in spite of much time being left.
This causes a tight loop, burning CPU cycles. To mitigate the issue, a short
100ms sleep is inserted, and the call is retried. Once this bug is fixed in
NaCl, this hack can be removed.