core: cli flag to disable grandpa (#2105)

* core: cli flag to disable grandpa

* core: fix test service configuration

* Update core/service/test/src/lib.rs

substrate/core/service/test/src/lib.rs

@@ -121,6 +121,7 @@ fn node_config<F: ServiceFactory> (
 		telemetry_endpoints: None,
 		default_heap_pages: None,
 		force_authoring: false,
+		disable_grandpa: false,
 	}
 }