fix pool timer leak bug, resolve#3353 (#3358)

When remove peer, block pool simple remove bpPeer,
but do not stop timer, that cause stopError for recorrected
peers. Stop timer when remove from pool.

blockchain/pool.go

@@ -299,6 +299,9 @@ func (pool *BlockPool) removePeer(peerID p2p.ID) {
 			requester.redo(peerID)
 		}
 	}
+	if p, exist := pool.peers[peerID]; exist && p.timeout != nil {
+		p.timeout.Stop()
+	}
 	delete(pool.peers, peerID)
 }