Fix cleanupMountpoint issue for Windows
Fix cleanupMountpoint issue for Windows

For windows, after unmount, the symlink is already removed. The previous
logic uses removePathIfNotMountPoint which will return error if
path no longer exist.

This PR add the logic to return no error after unmount and path is no
longer exist.

Change-Id: Ie90ee698c95c3d2f0db8f13e3a8761638424c066

Kubernetes-commit: 84c2a5518e78eb6ec9bc32c2239ae45d4b42007e

kubernetes/mount-utils