krb5_get_cred_from_kdc_opt returns KRB5_REALM_UNKNOWN instead of KRB5KDC_ERR_C_PRINCIPAL_UNKNOWN

[Ben Creech]

I don't know if anyone actually gets or pays attentions to notifications 
from RT, so I figured I'd repost this here:

<http://krbdev.mit.edu/rt/Ticket/Display.html?id=1735>