Comment 1 for bug 1676529

This was due to a switch in the default transport from multicast to unicast in the hacluster charm made for the 16.10 charm release:

  https://docs.openstack.org/developer/charm-guide/1610.html

although we did not have any detail about duplicate nodes in corosync at the link above.

The charm should probably make some sort of effort to cleanup the old nodes when switching between modes.