pkg/system: remove unused system.Unmount() utility

On Linux/Unix it was just a thin wrapper for unix.Unmount(), and a no-op on Windows.

This function was not used anywhere (also not externally), so removing this without
deprecating first.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

pkg/system/syscall_unix.go

@@ -1,11 +0,0 @@
-// +build linux freebsd
-
-package system // import "github.com/docker/docker/pkg/system"
-
-import "golang.org/x/sys/unix"
-
-// Unmount is a platform-specific helper function to call
-// the unmount syscall.
-func Unmount(dest string) error {
-	return unix.Unmount(dest, 0)
-}

pkg/system/syscall_windows.go

@@ -52,12 +52,6 @@ func IsWindowsClient() bool {
 	return osviex.ProductType == verNTWorkstation
 }
 
-// Unmount is a platform-specific helper function to call
-// the unmount syscall. Not supported on Windows
-func Unmount(_ string) error {
-	return nil
-}
-
 // HasWin32KSupport determines whether containers that depend on win32k can
 // run on this machine. Win32k is the driver used to implement windowing.
 func HasWin32KSupport() bool {