netfilter: nfnetlink_log: just returns error for unknown command

commit eb075954 upstream.

This patch stops processing options for unknown command.

Signed-off-by: Ken-ichirou MATSUZAWA <chamas@h4.dion.ne.jp>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Cc: Zubin Mithra <zsm@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Lee Jones <joneslee@google.com>
Change-Id: Ib2d04850f6324f5e944e60cbb64a83499ba94dd0