Bor fix rpcdeamon engine initialization

[mh0lt]

This fixes 2 related issues:

• Now that the bor consensus engine is required for queries it can't be created based on the pretense of a db directory, but must be based on chain config read from the db. Using the DB presence causes Bor to get instantiated for non bor chains which breaks.
• At the moment eth_calls on a remote daemon don't check Bor headers prior to calling the EVM code as it was just using a fake ETHash instance - which performs ETH header validation only.

The current version is mostly working but needs adapting to perform lazy initialization of the engine.