[krbdev.mit.edu #8596] kinit segfault with Heimdal server

[Greg Hudson via RT]

Nico reported this bug in April.  It was assigned #8573 (which I will 
merge this ticket into).  We fixed the encrypted challenge client code 
to check for no armor key on master, and marked the fix for pullup to 
the 1.15 and 1.14 release branches.  We haven't yet pulled up the fix to 
the release branches or issued patch releases, so it's not surprising 
that you would still see the bug in OS-packaged krb5 builds.

I agree that it is also weird that the client can walk down the preauth 
mechanisms via prompter interrupts (or other prompter failures), 
especially for these two mechanisms.  Your patch might be a good idea 
independent of this segfault bug; I will think about it.