MFC: r346190
Fix nfsdumpstate(8) so that it can print out INET6 callback addresses.

The patch adds support for printing of INET6 callback addresses.
It also adds the #ifdef INET, INET6 as requested by bz@.

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Add two new utilities and two new daemons to /usr/src/usr.sbin that
are specifically used by the experimental nfsv4 subsystem.
nfscbd - The NFSv4 client callback daemon.
nfsuserd - The NFSv4 daemon that maps between user and group name
and their corresponding uid/gid numbers.
nfsdumpstate - A utility that dumps out the NFSv4 Open/Lock state.
nfsrevoke - Administratively revokes an NFSv4 client, releasing all
NFSv4 Open/Lock state it holds on the server.

Approved by: kib (mentor)