On aufs, auplink is run before the Unmount. Irrespective of the result, we proceed to issue a Unmount syscall. In which case, demote erros on auplink to warning. Signed-off-by: Anusha Ragunathan <anusha@docker.com> Upstream-commit: dbd9b7e121c2e20e5429fdc97421c9510746161e Component: engine