BUG/MINOR: proxy: wake up all threads when sending the hard-stop signal

BUG/MINOR: proxy: wake up all threads when sending the hard-stop signal

The hard-stop event didn't wake threads up. In the past it wasn't an issue
as the poll timeout was limited to 1 second, but since commit 4f59d3861
("MINOR: time: increase the minimum wakeup interval to 60s") it has become
a problem because old processes can remain live for up to one minute after
the hard-stop-after delay. Let's just wake them up.

This may be backported to older releases, though before 2.4 the extra
delay was only one second.