Do not request the same prevote/precommit message to a peer

CodeChain propagates Prevote and Precommit messages using the following method: Node A tells Node B that it has vote 1, vote 2, and vote 3. Since node B has vote 1, node B ask node A to give vote 2 and vote 3.

Since CodeChain is not recording the vote requests, it can send the same requests to the same peer. If CodeChain can remember the old request, it will not send the same request again and as a result, we can reduce network usage.