password quality check in case the user changes the user's own password
kadm_chpass_with_key: disallow the user to change it own password to a
key, since that password might violate the password quality check.
git-svn-id: svn://svn.h5l.se/heimdal/trunk/heimdal@11626 ec53bebd-3082-4978-b11e-865c3cabbd6b