do not try any dns operations if there is local configuration
admin: fallback to kerberos.REALM
524: fallback to kdcs
kpasswd: fallback to admin
add some comments
git-svn-id: svn://svn.h5l.se/heimdal/trunk/heimdal@10071 ec53bebd-3082-4978-b11e-865c3cabbd6b