LU-9859 libcfs: remove unnecessary cfs_block_allsigs() calls

LU-9859 libcfs: remove unnecessary cfs_block_allsigs() calls

Threads started by kthread_run() ignore all signals,
as kthreadd() calls ignore_signals(), and this is
inherited by all children.
So there is no need to call cfs_block_allsigs() in functions
that are only run from kthread_run().

For the case of lnet_ping_md_unlink() it is not from a kernel
thread but nothing in that function should be affected by
signals so it is safe to remove.

For lnet_ping() we need to manually block signals since
LNetEQPool() can unconditionally abort when a signal is
recieved.

Linux-commit: 1b2dad1459e480028a2714439048d8a634132857

Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Change-Id: I124dccf78a3187d5f4a31c7b76db5369aaafc369
Reviewed-on: https://review.whamcloud.com/35350
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Neil Brown <neilb@suse.de>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Reviewed-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>