[krbdev.mit.edu #7809] klist displays bad error for nonexistent KEYRING ccache

[Greg Hudson via RT]

If the default cache has type KEYRING and does not exist, klist 
displays:

    klist: No credentials cache found while retrieving principal name

For a FILE ccache, klist displays:

    klist: No credentials cache found (ticket cache FILE:/pathname)

This is because file ccaches fail in krb5_cc_set_flags while keyring 
ccaches fail in krb5_cc_get_principal.

On a related note, klist doesn't have a com_err hook like kinit, so it 
ignores extended error messages.  If it did use extended messages, we 
would see the extended error message "Credentials cache file '/pathname' 
not found (ticket cache FILE:/pathname)", which would be redundant.