[NETFILTER] ip_conntrack: Update event cache when status changes

The GRE, SCTP and TCP protocol helpers did not call
ip_conntrack_event_cache() when updating ct->status.  This patch adds
the respective calls.

Signed-off-by: Harald Welte <laforge@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>