[krbdev.mit.edu #7892] mismatch between client keytab default principal for kinit and GSS-API

[Benjamin Kaduk via RT]

When client keytabs are used to automatically obtain initiator credentials for the GSS-API, we use 
the heuristic of picking the first krb5 principal in the keytab as the GSS identity to use for the 
initiator.  However, 'kinit -k -i', though it uses the client keytab, defaults to attempting to get 
credentials for host/[hostname].  This latter functionality is of questionable utility, and the 
inconsistency between the two scenarios has potential for confusion.  We should probably switch 
the kinit behavior to match the gssapi behavior.