Rewrite ipsec6_setspidx_inpcb() to match the logic in the (now) equivalent IPv4 counterpart.
Rewrite ipsec6_setspidx_inpcb() to match the logic in the
(now) equivalent IPv4 counterpart.

MFC after:	4 weeks

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase