Implements a `CachedPath` function on the volume plugin adapter that we call from the volume list function instead of `Path. If a driver does not implement `CachedPath` it will just call `Path`. Also makes sure we store the path on Mount and remove the path on Unmount. Signed-off-by: Brian Goff <cpuguy83@gmail.com> Upstream-commit: 9e6b1852a78eda6ed2cb255d6be8a0d0e5a5ca40 Component: engine