Add new versions of log_badauth gssrpc callbacks

libgssrpc supports two callbacks for gss_accept_sec_context failures
on servers (one for AUTH_GSS and one for AUTH_GSSAPI), which are
IPv4-specific.  Provide an alternate version which supplies the
transport handle instead of the address, so that we can get the
address via the file descriptor for TCP connections.

(cherry picked from commit 4c57a429760a3b3aa89938a13708742675f9548b)

ticket: 7770
Correctly log IPv6 addresses in kadmind

Define client_addr() in server_stubs.c and use it consistently in that
file and ipropd_svc.c to get the client address from a transport
handle.  In it, call getpeername() on the client socket and use
inet_ntop() on the result, instead of using inet_ntoa() on the IPv4
socket address.  Provide a log_badauth2 callback to GSSRPC, so that we
get a transport handle instead of an IPv4 socket address, and use
client_addr() within it instead of inet_ntoa().

(cherry picked from commit 5384f45e728957da20ecf82d8cf567945a2bbf6e)

ticket: 7770
version_fixed: 1.12
status: resolved