coreutils: Exclude CVE-2016-2781 from cve-check

http://git.savannah.gnu.org/cgit/coreutils.git/commit/?id=v8.27-101-gf5d7c0842



"Given runcon is not really a sandbox command, the advice is to use
`runcon ... setsid ...` to avoid this particular issue.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit 2d273b5a)
Signed-off-by: Steve Sakoman <steve@sakoman.com>