A few more mountd cleanups:

A few more mountd cleanups:
- Remove some horrible code that faked a "struct addrinfo" to be
  later passed to freeaddrinfo(). Instead, add a new group type
  "GT_DEFAULT" used to denote that the filesystem is exported to the
  world, and treat this case separately.
- Don't clear the AI_CANONNAME flag in a struct addrinfo returned
  by getaddrinfo. There's still a bit more struct addrinfo abuse
  left in here.
- Simplify do_mount() slightly by using an addrinfo pointer to keep
  track of the current address.