When the principal is retrieved from the database via libkadm5srv, the
keys are always decrypted, so the reported mkvno is always 0. Rather
than returning 0 and implying that the key in the database is not
encrypted, report the mkvno as unknown for right now.
A better fix is required to either not decrypt the keys when retrieving
get information or to get the mkvno before keys are decrypted.
Signed-off-by: Love Hornquist Astrand <lha@h5l.org>