A function that blockBrokers should call prior to returning a block to ensure it can maintain control
of the block request flow. e.g. TrustedGatewayBlockBroker will use this to ensure that the block
is valid from one of the gateways before assuming its work is done. If the block is not valid, it should try another gateway
and WILL consider the gateway that returned the invalid blocks completely unreliable.
A function that blockBrokers should call prior to returning a block to ensure it can maintain control of the block request flow. e.g. TrustedGatewayBlockBroker will use this to ensure that the block is valid from one of the gateways before assuming its work is done. If the block is not valid, it should try another gateway and WILL consider the gateway that returned the invalid blocks completely unreliable.