Lock the interface address list when searching for a matching interface by address, or when implementing 'me' rules on IPv6.  Prefer the field name if_addrhead to the macro if_addrlist.
Lock the interface address list when searching for a matching interface
by address, or when implementing 'me' rules on IPv6.  Prefer the field
name if_addrhead to the macro if_addrlist.

MFC after:	2 weeks

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