LU-12678 socklnd: use need_resched()

LU-12678 socklnd: use need_resched()

Rather than using a counter to decide when to drop the lock and see if
we need to reshedule we can use need_resched(), which is a precise
test instead of a guess.

Test-Parameters: trivial testlist=sanity-lnet
Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: If13871a4a4c57ca87cbb1e22af85cb7fd24ab006
Reviewed-on: https://review.whamcloud.com/39128
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Reviewed-by: Chris Horn <chris.horn@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>