Nodes shouldn't join the committee until they are synced

[JamesHinshelwood]

Nodes send a JoinCommittee request as soon as they realise they are not part of the network. However, they may take some time after this downloading blocks and catching up with the chain. In this period, they can be elected as the block proposer, but they are unable to make a proposal. They shouldn't do this and instead wait until they are synced until joining.