Prior to this commit, if you ran Vagrant in a different current working
directory other than where a current guest machines location is, the
file provisioner would not take into account the machines local dir, and
would instead use the path where Vagrant was invoked to expand the
`source` path option for a file provisioner. This commit fixes that by
passing the root path `machine.env.cwd` when expanding the source dir.
0a6c4e2d0f