Please update the last places in the code where gethostbyaddr() and gethostbyname() are used, especially in the Kerberos user space utility with getaddrinfo() and getnameinfo().

That will make Lustre compatible with the /etc/gai.conf file that gives control over how these calls return info, especially ordering of IP address when a DNS host has multiple IP addresses.

(see man gai.conf)
 

CONFORMING TO
POSIX.1-2001  specifies  gethostbyname(), gethostbyaddr(), sethostent(), endhostent(), gethostent(), and h_errno; gethostbyname(), gethostbyaddr(), and h_errno are marked obsolescent in that standard. 
POSIX.1-2008 removes the specifications of gethostbyname(), gethostbyaddr(), and h_errno, recommending the use of getaddrinfo(3) and getnameinfo(3) instead.

This is simple enough that this ticket could be handled by somebody which is not a Kerberos expert.