[krbdev.mit.edu #6716] preauth mech duality causes havoc

[Jeff Blaine via RT]

Based on 1.8 source, defining the same ID for 2 preauth mechs
causes kinit to segfault (and probably other things!)

"(2:00:59 PM) ghudson: I can't tell from that description whether that's 
a bug in our code or one you introduced.  It sounds like it might be a 
bug in our code."

So here's the more detailed description.

# grep -h 'define KRB5_PADATA' plugins/preauth/myplugin/myplugin_main.c 
plugins/preauth/cksum_body/cksum_body_main.c
#define KRB5_PADATA_MYPLUGIN 130
#define KRB5_PADATA_CKSUM_BODY_REQ 130

# alias kdc
alias kdc='pkill krb5kdc; sleep 1; /usr/mykrb/sbin/krb5kdc -r 
MYREALM.OUR.ORG; ps -ef | grep krb5kdc | grep -v grep'
# kdc
root     19763     1  0 14:09 ?        00:00:00 /usr/mykrb/sbin/krb5kdc 
-r MYREALM.OUR.ORG
#

> kinit jblaine at MYREALM.OUR.ORG
Segmentation fault
>