Add logging when recv_message can't parse an inbound message

[achamayou]

This is currently logged:

Exception in virtual void aft::Aftconsensus::LedgerEnclave::recv_message(const ccf::NodeId
&, const uint8_t *, size_t) [LedgerProxy = consensus::LedgerEnclave]

But the payload is encrypted, and so is safe to log while being potentially helpful in understanding how the traffic ends up there.