get_users doesn’t return the resource names. The list shows different users but not the different resources of a single user.
Regarding the configs for setting the policy to drop the old connection I found this:
http://jabber.996255.n3.nabble.com/resource-conflict-td31971.html
The link says, you can set the policy to close the old session by adding this to the configs:
{resource_conflict, closeold}.
