Sent to a WIMMessageCallback function to indicate that an image is being unmounted as part of the cleanup process.
WIM_MSG_CLEANUP_UNMOUNTING_IMAGE wParam = (PWSTR) MountPath; lParam = (DWORD) State;
[in] Specifies the driver path of the image being unmounted.
[in] Indicates whether the operation has completed. A non-zero value indicates that the unmount has completed.
Your routine must return WIM_MSG_SUCCESS.