Windows: Refactor configs/cgroup.go

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

libcontainer/configs/cgroup_unix.go

@@ -1,3 +1,5 @@
+// +build linux freebsd
+
 package configs
 
 type FreezerState string
@@ -8,9 +10,6 @@ const (
 	Thawed    FreezerState = "THAWED"
 )
 
-// TODO Windows: This can be factored out in the future as Cgroups are not
-// supported on the Windows platform.
-
 type Cgroup struct {
 	Name string `json:"name"`
 

libcontainer/configs/cgroup_windows.go

@@ -0,0 +1,6 @@
+package configs
+
+// TODO Windows: This can ultimately be entirely factored out on Windows as
+// cgroups are a Unix-specific construct.
+type Cgroup struct {
+}