LU-9859 libcfs: discard cfs_block_sigsinv()

LU-9859 libcfs: discard cfs_block_sigsinv()

cfs_block_sigsinv() and cfs_restore_sigs() are simple
wrappers which save a couple of line of code and
hurt readability for people not familiar with them.
They aren't used often enough to be worthwhile,
so discard them and open-code the functionality.

The sigorsets() call isn't needed as or-ing with current->blocked is
exactly what sigprocmask(SIG_BLOCK) does.

Linux-commit: 6afe572bc76688cd840032254217a4877b66e916

Change-Id: Ia9189e0885dffb098df7abef09db42ecb49196cd
Signed-off-by: Mr NeilBrown <neilb@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-on: https://review.whamcloud.com/38530
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>