Updates:

• TX is validated before broadcast (using mempool test).
• The sender ignores incoming messages from the receiver (except the handshake and PONG), so the sender cannot send back the tx before disconnection.
• When it receives the tx back, it becomes "just a tx in mempool".

TODO/NICE TO HAVE

• Check if the wallet is going to rebroadcast a tx it has created but has been broadcast via private broadcast and if yes, prevent that.
• Consider disabling walletbroadcast=1 if privatebroadcast=1, or in other words - enforce walletbroadcast=0.
• RPC to check the stats.