add locking assertions that turn into noops if INET6 is configured; this is necessary because the ipv6 code shares the in_pcb code with ipv4 but (presently) lacks proper locking
add locking assertions that turn into noops if INET6 is configured;
this is necessary because the ipv6 code shares the in_pcb code with
ipv4 but (presently) lacks proper locking

Supported by:	FreeBSD Foundation

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