Convert ListImages to use reauth.

This commit does not work -- acceptance test 08-... is broken.
diff --git a/reauth_test.go b/reauth_test.go
index 62d3e7e..e6ccb17 100644
--- a/reauth_test.go
+++ b/reauth_test.go
@@ -110,6 +110,9 @@
 func (my *MyAccess) Revoke(string) error {
 	return nil
 }
+func (my *MyAccess) Reauthenticate() error {
+	return nil
+}
 
 func TestReauthHandlerUsesSameAccessProvider(t *testing.T) {
 	fakeAccess := &MyAccess{}