The purpose is to unblock previously blocked SIGCHLD, not all the
signals. IIRC, this block-unblock dancing is about a race where SIGCHLD
may come during switching to restorer blob, where CRIU handler function
is already unmapped - which will result in segmentation violation if
SIGCHLD wasn't blocked.

Fixes:3a61c38a ("restore: block sigchld to remap task_entries")

Cc: Andrei Vagin <avagin@virtuozzo.com>
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>