Reduce grandpa interval for substrate node (#2097)

substrate/node/cli/src/service.rs

@@ -106,7 +106,7 @@ construct_service_factory! {
 					grandpa::Config {
 						local_key,
 						// FIXME #1578 make this available through chainspec
-						gossip_duration: Duration::new(4, 0),
+						gossip_duration: Duration::from_millis(333),
 						justification_period: 4096,
 						name: Some(service.config.name.clone())
 					},