[OpenAFS] afs/cell@REALM vs afs@REALM vs 1.5.68

[Adam Megacz]

Many AFS tools will accept either of these two principals for the
vlserver/dbserver/fileserver:

  afs/cell@REALM
       afs@REALM

Is one preferred over the other for new cells?

Moreover, there seems to be some sort of change in the behavior of the
1.5.68 aklog relative to 1.4.11; the new aklog only appears to attempt
the latter one.

  - a