cleanup error handling on mode change failure. TODO: non-IPv4 kernel support should be improved. "netstat" should be okay, "inet.ip" and "inet.icmp" needs more trick. NetBSD PR: 9157
Suggested by: Andy Doran <ad@mr-magoo.sports.gov.uk> - inet6.ip6 and ipsec menu - u_quad_t printing fix - #ifdefs to allow compilation on 1.4.x