openvswitch: Remove incorrect WARN_ONCE().

ovs_ct_find_existing() issues a warning if an existing conntrack entry
classified as IP_CT_NEW is found, with the premise that this should
not happen.  However, a newly confirmed, non-expected conntrack entry
remains IP_CT_NEW as long as no reply direction traffic is seen.  This
has resulted into somewhat confusing kernel log messages.  This patch
removes this check and warning.

Fixes: 289f2253

 ("openvswitch: Find existing conntrack entry after upcall.")
Suggested-by: Joe Stringer <joe@ovn.org>
Signed-off-by: Jarno Rajahalme <jarno@ovn.org>
Acked-by: Joe Stringer <joe@ovn.org>
Signed-off-by: David S. Miller <davem@davemloft.net>