MFC rev 1.163:   Clean up after tun(4) properly; remove routes whose ifp is set to   that of the tun instance even for the !AF_INET case, and properly   remove configured addresses by calling if_purgeaddrs().
MFC rev 1.163:
  Clean up after tun(4) properly; remove routes whose ifp is set to
  that of the tun instance even for the !AF_INET case, and properly
  remove configured addresses by calling if_purgeaddrs().

  Maintain the TUN_DSTADDR behaviour for compatibility with the OS/390
  emulator.

PR:		100080
Reviewed by:	bz

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