LU-10467 lustre: don't use l_wait_event() for simple sleep.

LU-10467 lustre: don't use l_wait_event() for simple sleep.

Passing '0' as the condition to l_wait_event() means that
it just waits for the given timeout.
This can be done more simply with ssleep(seconds) or in
one case, a schedule_timeout_killable() loop.

In most of these case, l_wait_event() in configured to ignore signals,
so ssleep() - which also ignores signals - is appropriate.
In one case (lfsck_lib.c) l_wait_event() is configured to respond
to fatal signals, and as there is no ssleep_killable, we
need to opencode one.

ssleep() and schedule_timeout_killable() *will* add to the load
average, while l_wait_event() does not, so if these sleeps happen a
lot, it will add to the load average.  I don't think that will be a
problem for these sleeps.

So remove these l_wait_event() calls and associated variables,
and do it the simpler ways.

Signed-off-by: Mr NeilBrown <neilb@suse.com>
Change-Id: I5a77e631c68f6dfb45fdd7ea01d60b13268240cc
Reviewed-on: https://review.whamcloud.com/35966
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Shaun Tancheff <stancheff@cray.com>
Reviewed-by: Petros Koutoupis <pkoutoupis@cray.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>