svc/conntrack.in: Contemplate multiple address families.

svc/conntrack.in: Contemplate multiple address families.

A number of relatively simple changes, with no overall functional change
except for a few diagnostic messages.

  * Attach the address-family code and a name string to the
    `InetAddress' class.  This will mean that we can add new address
    families without breaking things.

  * Make `testaddrs' (and related variables) be a dictionary, mapping
    address families to addresses, rather than just a lone address.

  * Ensure that the networks in a peer assignment belong to the same
    family.  They will do for now, because there's only one.

  * Have `kickpeers' maintain a local IP address for each family, rather
    than just a single one.