I split this up into three other tickets: #7740 for kadmind accepting 
anonymous names, #7741 for kadmin -n choosing an appropriate principal, 
and #7743 for the ability to add a principal and extract its random key.

I was not able to reproduce any sporadic failures.  If we get enough 
information about such failures to have a hope of debugging it, we can 
open a new issue about it.