container/init: configure interface lo

This enables loopback networking when owning the net namespace.

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

container/dispatcher_test.go

@@ -465,6 +465,8 @@ func (k *kstub) ensureFile(name string, perm, pperm os.FileMode) error {
 		stub.CheckArg(k.Stub, "pperm", pperm, 2))
 }
 
+func (*kstub) mustLoopback(message.Msg) { /* noop */ }
+
 func (k *kstub) seccompLoad(rules []std.NativeRule, flags seccomp.ExportFlag) error {
 	k.Helper()
 	return k.Expects("seccompLoad").Error(