dhcp_server_handle_message: don't pretend there was a difference between return code 0 or 1

We ignore the difference anyway, hence let's systematically return 0.

src/libsystemd-network/sd-dhcp-server.c

@@ -942,12 +942,10 @@ int dhcp_server_handle_message(sd_dhcp_server *server, DHCPMessage *message,
                         server->bound_leases[pool_offset] = NULL;
                         hashmap_remove(server->leases_by_client_id, existing_lease);
                         dhcp_lease_free(existing_lease);
+                }
 
-                        return 1;
-                } else
                 return 0;
-        }
-        }
+        }}
 
         return 0;
 }