Fix pr_player() and upr_player() to obey max_idle

Fix pr_player() and upr_player() to obey max_idle

The output queue flush can block indefinitely.  Permits a client to
hog the thread indefinitely by not reading output.

Broken in commit 08b94556 (v4.3.20) "Reimplement max_idle without a
separate thread".  Until then, the idle thread aborted a stuck attempt
to flush output.

Denial of service seems possible.