netfilter: nf_conntrack: Support expectations in different zones

When zones were originally introduced, the expectation functions were
all extended to perform lookup using the zone. However, insertion was
not modified to check the zone. This means that two expectations which
are intended to apply for different connections that have the same tuple
but exist in different zones cannot both be tracked.

Fixes: 5d0aa2cc (netfilter: nf_conntrack: add support for "conntrack zones")
Signed-off-by: Joe Stringer <joestringer@nicira.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>