Summary:
Paths are not necessarily legal glob syntax. In particular, backslash
is used for escaping. This caused problems on Windows, where we tried
to pass a backslash-delimited path into `eden prefetch --no-prefetch`.

Reviewed By: xavierd

Differential Revision: D25072784

fbshipit-source-id: 9ce8e5ccc8f28581512c39d04922889da0bc1bf6