network/consensus: use new dbft StopTxFlow callback

It makes sense in general (further narrowing down the time window when
transactions are processed by consensus thread) and it improves block times a
little too, especially in the 7+2 scenario.

Related to #2744.

cli/server/server.go

@@ -332,6 +332,7 @@ func mkConsensus(config config.Wallet, tpb time.Duration, chain *core.Blockchain
 		Chain:                 chain,
 		ProtocolConfiguration: chain.GetConfig(),
 		RequestTx:             serv.RequestTx,
+		StopTxFlow:            serv.StopTxFlow,
 		Wallet:                &config,
 		TimePerBlock:          tpb,
 	})