[login_manager] Add stub DBus API for policy get/set

interface.h

Index: interface.h
diff --git a/interface.h b/interface.h
index b5ffaf0e10cc6c8d738a71a202bb80cd03807206..9e8eb04565af704ba46cbc5cd622533f67f603ea 100644
--- a/interface.h
+++ b/interface.h
@@ -80,6 +80,14 @@ gboolean session_manager_retrieve_property(SessionManager *self,
                                            gchar **OUT_value,
                                            GArray **OUT_signature,
                                            GError **error);
+gboolean session_manager_store_policy(SessionManager *self,
+                                      gchar *policy_blob,
+                                      GArray *signature,
+                                      GError **error);
+gboolean session_manager_retrieve_policy(SessionManager *self,
+                                         gchar **OUT_policy_blob,
+                                         GArray **OUT_signature,
+                                         GError **error);
 
 gboolean session_manager_unlock_screen(SessionManager *self,
                                        GError **error);