Make hive use IPC connection

[holiman]

From what I can tell; https://github.com/karalabe/hive/blob/master/simulator.go#L309 , the simulator uses the ip:8545 to connect to the client API. This is a bit problematic for cpp: ethereum/aleth#4635 (comment)

We recently removed HTTP server from eth, now instead of --json-rpc --json-rpc-port 8545 --admin-via-http you need to run scripts/jsonrpcproxy.py

Doing it this way requires us to add python to the alpine image, so it'd be neat to just use the ipc path instead.

[fjl]

We cannot do this because some clients don't support IPC. JSON-RPC over HTTP is the lowest common denominator interface.