make SSH key and host nodes dir available

The Vagrant provider requires an SSH key and the ability to read from a folder to get all nodes available in the cluster. Without it, it will fail to provision new nodes.
add empty host_nodes_dir
fix typo
Revert "add empty host_nodes_dir"

This reverts commit 99a43defd92f3f4cbab30a3a0a08c656622a11cc.
fix path issue
Merge pull request #661 from opdemand/655-vagrant-nodes

make SSH key and host nodes dir available