Fix a bug in IPv4 address configuration exposed by refcounting.  * Join the IPv4 all-hosts multicast group 224.0.0.1 once only;    that is, when an IPv4 address is first configured on an interface.  * Do not join it for subsequent IPv4 addresses as this violates IGMP.  * Be sure to leave the group when all IPv4 addresses have been removed    from the interface.  * Add two DIAGNOSTIC printfs related to the issue.
Fix a bug in IPv4 address configuration exposed by refcounting.
 * Join the IPv4 all-hosts multicast group 224.0.0.1 once only;
   that is, when an IPv4 address is first configured on an interface.
 * Do not join it for subsequent IPv4 addresses as this violates IGMP.
 * Be sure to leave the group when all IPv4 addresses have been removed
   from the interface.
 * Add two DIAGNOSTIC printfs related to the issue.

Further care and attention is needed in this area; it is suggested that
netinet's attachment to the ifnet structure be compartmentalized and
non-implicit.

Bug found by:	andre
MFC after:	1 month

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