LU-10467 lfsck: use wait_event_idle()

LU-10467 lfsck: use wait_event_idle()

This l_wait_event() call is equivalent to the more standard
wait_event_idle().
So switch over to wait_event_idle().

Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: I8e13360a40dd1eec740f597d649c0f230533eb3d
Reviewed-on: https://review.whamcloud.com/37610
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>