Currently we log Transaction is mined for every local (own) transaction that is dropped from the queue.
In fact it's not always true, if the same key is used on some other nodes or if we send multiple replacement transactions (bumping gas price, but using the same nonce) - the transaction might be removed, but some other transaction with the same (sender, nonce) was actually included in the blockchain.

This PR attempts to fix the logging for local transactions by checking if the transaction is in chain before printing the log line.

Since we don't have a client instance in the miner, we do that by using a Weak reference (to prevent cyclic references).