Clean up logs (#1541)

## Description

This PR improves some logging for the end-user. 

It downgrades some warning logs and removes the slots per second sync speed if we are syncing and the speed is 0. This is likely because we are syncing from a finalised checkpoint and the head doesn't change.

beacon_node/client/src/notifier.rs

@@ -122,14 +122,28 @@ pub fn spawn_notifier<T: BeaconChainTypes>(
                     head_distance.as_u64(),
                     slot_distance_pretty(head_distance, slot_duration)
                 );
+
+                let speed = speedo.slots_per_second();
+                let display_speed = speed.map_or(false, |speed| speed != 0.0);
+
+                if display_speed {
                     info!(
                         log,
                         "Syncing";
                         "peers" => peer_count_pretty(connected_peer_count),
                         "distance" => distance,
-                    "speed" => sync_speed_pretty(speedo.slots_per_second()),
+                        "speed" => sync_speed_pretty(speed),
                         "est_time" => estimated_time_pretty(speedo.estimated_time_till_slot(current_slot)),
                     );
+                } else {
+                    info!(
+                        log,
+                        "Syncing";
+                        "peers" => peer_count_pretty(connected_peer_count),
+                        "distance" => distance,
+                        "est_time" => estimated_time_pretty(speedo.estimated_time_till_slot(current_slot)),
+                    );
+                }
             } else if sync_state.is_synced() {
                 let block_info = if current_slot > head_slot {
                     "   …  empty".to_string()
@@ -220,14 +234,37 @@ fn seconds_pretty(secs: f64) -> String {
     let hours = d.whole_hours();
     let minutes = d.whole_minutes();
 
+    let week_string = if weeks == 1 { "week" } else { "weeks" };
+    let day_string = if days == 1 { "day" } else { "days" };
+    let hour_string = if hours == 1 { "hr" } else { "hrs" };
+    let min_string = if minutes == 1 { "min" } else { "mins" };
+
     if weeks > 0 {
-        format!("{:.0} weeks {:.0} days", weeks, days % DAYS_PER_WEEK)
+        format!(
+            "{:.0} {} {:.0} {}",
+            weeks,
+            week_string,
+            days % DAYS_PER_WEEK,
+            day_string
+        )
     } else if days > 0 {
-        format!("{:.0} days {:.0} hrs", days, hours % HOURS_PER_DAY)
+        format!(
+            "{:.0} {} {:.0} {}",
+            days,
+            day_string,
+            hours % HOURS_PER_DAY,
+            hour_string
+        )
     } else if hours > 0 {
-        format!("{:.0} hrs {:.0} mins", hours, minutes % MINUTES_PER_HOUR)
+        format!(
+            "{:.0} {} {:.0} {}",
+            hours,
+            hour_string,
+            minutes % MINUTES_PER_HOUR,
+            min_string
+        )
     } else {
-        format!("{:.0} mins", minutes)
+        format!("{:.0} {}", minutes, min_string)
     }
 }
 

beacon_node/network/src/beacon_processor/chain_segment.rs

@@ -81,7 +81,7 @@ pub fn handle_chain_segment<T: BeaconChainTypes>(
             // reverse
             match process_blocks(chain, downloaded_blocks.iter().rev(), &log) {
                 (_, Err(e)) => {
-                    warn!(log, "Parent lookup failed"; "last_peer_id" => format!("{}", peer_id), "error" => e);
+                    debug!(log, "Parent lookup failed"; "last_peer_id" => format!("{}", peer_id), "error" => e);
                     sync_send
                         .send(SyncMessage::ParentLookupFailed{peer_id, chain_head})
                         .unwrap_or_else(|_| {

beacon_node/network/src/beacon_processor/mod.rs

@@ -774,6 +774,13 @@ impl<T: BeaconChainTypes> BeaconProcessor<T> {
                                     );
                                     return;
                                 }
+                                Err(BlockError::BlockIsAlreadyKnown) => {
+                                    debug!(
+                                        log,
+                                        "Gossip block is already known";
+                                    );
+                                    return;
+                                }
                                 Err(e) => {
                                     warn!(
                                         log,