conntrack: Fix conntrack new state

conntrack: Fix conntrack new state

In connection tracking system, a connection is established if we
see packets from both directions.  However, in userspace datapath's
conntrack, if we send a connection setup packet in one direction
twice, it will make the connection to be in established state.

This patch fixes the aforementioned issue, and adds a system traffic
test for UDP and TCP traffic to avoid regression.

Fixes: a489b16854b59 ("conntrack: New userspace connection tracker.")
Signed-off-by: Yi-Hung Wei <yihung.wei@gmail.com>
Signed-off-by: William Tu <u9012063@gmail.com>