consensus: fixes #1754

* updateToState exits early if the state isn't new, which happens after
* fast syncing. This results in not sending a NewRoundStep message. The mempool
* reactor depends on PeerState, which is updated by NewRoundStep
* messages. If the peer never sends a NewRoundStep, the mempool reactor
* will think they're behind, and never forward transactions. Note this
* only happens when `create_empty_blocks = false`, because otherwise
* peers will move through the consensus state and send a NewRoundStep
* for a new step soon anyways. Simple fix is just to send the
* NewRoundStep message during updateToState even if exit early

mempool/mempool.go

@@ -328,11 +328,11 @@ func (mem *Mempool) notifyTxsAvailable() {
 		panic("notified txs available but mempool is empty!")
 	}
 	if mem.txsAvailable != nil && !mem.notifiedTxsAvailable {
+		// channel cap is 1, so this will send once
 		select {
 		case mem.txsAvailable <- mem.height + 1:
 		default:
 		}
-
 		mem.notifiedTxsAvailable = true
 	}
 }