Support jsonrpc-addr for tesnet

[kennyrowe]

add support for jsonrpc-addr for private testnet

[kennyrowe]

I also removed --nodiscover but only because I found it useful to spin up the same configuration on multiple machines.

[rainbreak]

@kennyrowe can you expand on the use case here? You're doing a networked local testnet or something?

[kennyrowe]

@rainbreak yeah networked testnet. Spun up a testnet and connected it to MetaMask to play with a dapp. Since it’s networked and can test with multiple participants at the same time or asynchronously depending on the dapp.