BUG/MEDIUM: haterm: Properly handle client timeout

BUG/MEDIUM: haterm: Properly handle client timeout

No client timeout was set with haterm. It could be an issue with
unresponsive clients. So the I/O timeout of the SC is initialized to the
frontend client timeout when the hstream is created. Then a read activity is
reported when data are received. This read activity is used to set an
expiration date on the hstream task and test it when the hstream is woken up
with TASK_WOKEN_TIMER reason.

When a client timeout is detected, the hstream try to send a 408 and report
an error.