jail - Fix broken port matching code

jail - Fix broken port matching code

* in_pcblookup_local() and in_pcblookup_localremote() were trying to
  use the cred to distinguish between jails, but these routines are used
  to locate a free port for bindind purposes and could wind up returning
  a lookup failure for an occupied port.

  The code may have been present in an early isolation attempt for jails.

* Remove the code.  Isolating the IPs for a jail basically requires using
  IP aliases, not by trying to isolate port number sets between jails.