During a plugin remove, docker performs an `os.Rename` to move the
plugin data dir to a new location before removing to acheive an atomic
removal.
`os.Rename` can return either a `NotExist` error if the source path
doesn't exist, or an `Exist` error if the target path already exists.
Both these cases can happen when there is an error on the final
`os.Remove` call, which is common on older kernels (`device or resource
busy`).
When calling rename, we can safely ignore these error types and proceed
to try and remove the plugin.
Signed-off-by: Brian Goff <cpuguy83@gmail.com>
