syncing nodes communicate with the current hbbft set.

[SurfingNerd]

example on alpha testnet:

2023-07-10 20:06:10  Worker devp2p2 TRACE consensus  Cached Messages: Trying to send cached messages to 0xd66dfb161550df9dd259a6495dec9e80a8dc66b94b377c9b0339d960035c9084201ead161eddb81f96b3424d5e3fa4d33931e4c72eaa666a50db89e776285244
2023-07-10 20:06:11  Worker Client2 TRACE consensus  Received message of idx 17  Message { epoch: 380988, content: Subset(Message { proposer_id: fc..f4, content: Broadcast(Echo(Proof { #8, root_hash: 59b6..e9cf, value: 2024..6d1a, .. })) }) } from NodeId(0xd66d…5244)
2023-07-10 20:06:11  Worker Client1 TRACE consensus  Received message of idx 24  Message { epoch: 9160, content: Subset(Message { proposer_id: f5..51, content: Broadcast(Value(Proof { #24, root_hash: 3ebe..4c63, value: 83fc..e3d5, .. })) }) } from NodeId(0xf515…bb51)
2023-07-10 20:06:11  Worker Client3 TRACE consensus  Received message of idx 25  Message { epoch: 9160, content: Subset(Message { proposer_id: f5..51, content: Broadcast(Echo(Proof { #22, root_hash: 3ebe..4c63, value: e335..e829, .. })) }) } from NodeId(0xf515…bb51)
2023-07-10 20:06:13  Worker Client2 TRACE consensus  Received message of idx 24  Message { epoch: 345, content: Subset(Message { proposer_id: 9f..f6, content: Broadcast(Value(Proof { #24, root_hash: c7f4..b494, value: 1ded..8659, .. })) }) } from NodeId(0x9f49…b8f6)
2023-07-10 20:06:13  Worker Client3 TRACE consensus  Received message of idx 25  Message { epoch: 345, content: Subset(Message { proposer_id: 9f..f6, content: Broadcast(Echo(Proof { #13, root_hash: c7f4..b494, value: 3f09..1a88, .. })) }) } from NodeId(0x9f49…b8f6)

it looks like that the nodes that are currently syncing are sending hbbft messages.
this is unexpected behavior.
a Node that is currently in a sync process should not send hbbft messages.

[SurfingNerd]

This should help: #73