cmd/app: use ephemeral overlay root

This replaces autoroot.

Signed-off-by: Ophestra <cat@gensokyo.uk>

cmd/app/app.go

@@ -55,8 +55,8 @@ func parse(id string, base *check.Absolute, r io.Reader) (*hst.Config, error) {
 					Target: fhs.AbsRoot,
 					Lower: []*check.Absolute{
 						base.Append("template", "initial"),
-						base.Append("template", "upper"),
 					},
+					Upper: base.Append("template", "upper"),
 				}},
 				{FilesystemConfig: &hst.FSBind{
 					Target: home,

cmd/app/app_test.go

@@ -75,8 +75,8 @@ talk com.canonical.Unity
 						Target: fhs.AbsRoot,
 						Lower: []*check.Absolute{
 							base.Append("template", "initial"),
-							base.Append("template", "upper"),
 						},
+						Upper: base.Append("template", "upper"),
 					}},
 					{FilesystemConfig: &hst.FSBind{
 						Target: hst.AbsPrivateTmp.Append("home"),