kcc: Allow RODC to be included in intersite topology

kcc: Allow RODC to be included in intersite topology

This creates behaviour not described by ADTS. RODC are now treated as
RED, however they are demoted to the equivalent of WHITE when running
the first half of the algorithm.

The change implies that RED does in fact refer to full-replicas, not
writable replicas.

Signed-off-by: Garming Sam <garming@catalyst.net.nz>
Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>