Improve vagrant hostname support across cluster

This PR makes the following changes:

1. minion identifiers are now of the form "kubernetes-minion-1", "kubernetes-minion-2"
2. fixes host ip not being returned properly in the kubecfg list pods operation
3. vagrant etcd storage paths no longer need to use hostname_override
4. ability to ping by host name each node in cluster from every other node
While perhaps we should change this, it seems risky enough and separate enough that it should be in a different PR.  For now, if you want to stop setting hostname_override you can stop defining the minion_ip grain.

If we do change this, making this be `kubernetes_node_name` might be better.