LU-10467 lustre: use wait_event_idle_timeout() as appropriate.

LU-10467 lustre: use wait_event_idle_timeout() as appropriate.

If l_wait_event() is passed an lwi initialised with
one of
   LWI_TIMEOUT_INTR( time, NULL, NULL, NULL)
   LWI_TIMEOUT_INTR( time, NULL, LWI_ON_SIGNAL_NOOP, NULL)
   LWI_TIMEOUT( time, NULL, NULL)
where time != 0, then it behaves much like
wait_event_idle_timeout().
All signals are blocked, and it waits either for the
condition to be true, or for the timeout (in jiffies).

Note that LWI_ON_SIGNAL_NOOP has no effect here.

l_wait_event() returns 0 when the condition is true, or -ETIMEDOUT
when the timeout occurs.  wait_event_idle_timeout() instead returns a
positive number when the condition is true, and 0 when the timeout
occurs.  So in the cases where return value is used, handling needs to
be adjusted accordingly.

Note that in some cases where cfs_fail_val gives the time to wait for,
the current code re-tests the wait time against zero as cfs_fail_val
can change asynchronously.  This is because l_wait_event() behaves
quite differently if the timeout is zero.

The new code doesn't need to do that as wait_event_idle_timeout()
treat 0 just as a very short wait, which is exactly the correct
behavior here.

This patch also removes a comment which is no longer meaningful
(CAN_MATCH) and corrects a debug message which reported the wait time
as "seconds" rather than the correct "jiffies".

This patch doesn't change the timed wait in cl_sync_io_wait().
That is a bit more complicated, so it left to a separate patch.

Change-Id: I632afc290935e321926f45b144d5367799a01381
Signed-off-by: Mr NeilBrown <neilb@suse.com>
Reviewed-on: https://review.whamcloud.com/35977
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Shaun Tancheff <stancheff@cray.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Petros Koutoupis <pkoutoupis@cray.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>