netfilter: ctnetlink: always honor CTA_MARK_MASK

Useful to only set a particular range of the conntrack mark while
leaving existing parts of the value alone, e.g. when updating
conntrack marks via netlink from userspace.

For NFQUEUE it was already implemented in commit 534473c6
("netfilter: ctnetlink: honor CTA_MARK_MASK when setting ctmark").

This now adds the same functionality also for the other netlink
conntrack mark changes.

Signed-off-by: Andreas Jaggi <andreas.jaggi@waterwave.ch>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>