Fix Tendermint deadlock (#4654)

* scope read

* consistent step

ethcore/src/engines/tendermint/mod.rs

@@ -151,12 +151,12 @@ impl Tendermint {
 	fn generate_message(&self, block_hash: Option<BlockHash>) -> Option<Bytes> {
 		let h = self.height.load(AtomicOrdering::SeqCst);
 		let r = self.view.load(AtomicOrdering::SeqCst);
-		let s = self.step.read();
-		let vote_info = message_info_rlp(&VoteStep::new(h, r, *s), block_hash);
+		let s = *self.step.read();
+		let vote_info = message_info_rlp(&VoteStep::new(h, r, s), block_hash);
 		match self.signer.sign(vote_info.sha3()).map(Into::into) {
 			Ok(signature) => {
 				let message_rlp = message_full_rlp(&signature, &vote_info);
-				let message = ConsensusMessage::new(signature, h, r, *s, block_hash);
+				let message = ConsensusMessage::new(signature, h, r, s, block_hash);
 				let validator = self.signer.address();
 				self.votes.vote(message.clone(), &validator);
 				debug!(target: "engine", "Generated {:?} as {}.", message, validator);