[NETFILTER]: nf_conntrack_sctp: rename "newconntrack" variable

The name is misleading, it holds the new connection state, so rename it
to "newstate". Also rename "oldsctpstate" to "oldstate" for consistency.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>