As newoe-18-poc-poc, but now the ping bursts out a few packets so that
there are packets during the initial IKE. This test case should show
that there are two IPsec SA's started. Since this uses AUTH_NULL, the
two cannot be distinguished from different users so they are not allowed
to replace each other (unlike in the case of non-AUTH_NULL)

  icmp ->  X
  IKE_INIT_REQ A ->
   icmp ---->
               X <-- icmp reply
            <- IKE_INIT_REQ B

two IPsec SA's establish


Note: this test seems vulnerable to a race condition where one connection is already terminated?

Note2: Is this premise true? It seems negotiationshunt=passthrough might not
work as expected with XFRM/NETKEY?  That is what this test now shows.