Windows - Really fix VFS this time

Signed-off-by: John Howard <jhoward@microsoft.com>

daemon/graphdriver/vfs/driver.go

@@ -1,4 +1,4 @@
-// +build linux
+// +build linux windows
 
 package vfs
 

daemon/graphdriver/vfs/driver_unsupported.go

@@ -1,3 +1,3 @@
-// +build !linux
+// +build !linux,!windows
 
 package vfs