make generic HCFS as under filesystem; setup VM environment for under filesystem unit tests

This make generic HCFS as under filesystem.

The unit test environment for Cephfs and Glusterfs is created by vagrant, detailed information can be found at vagrant/{ceph,glusterfs}/README.md.

@uronce-cc Thanks for the docker addition, you beat me on speed. If you like to add ceph and gluster integration, please let me know how i can help.