r18006: Actually a smaller change than it looks. Leverage

r18006: Actually a smaller change than it looks. Leverage
the get_dc_list code to get the _kerberos. names
for site support. This way we don't depend on one
KDC to do ticket refresh. Even though we know it's
up when we add it, it may go down when we're trying
to refresh.
Jeremy.
(This used to be commit 77fe2a3d7418012a8dbfb6aaeb2a8dd57c6e1a5d)