Integration Test for RPC nodes

Write a new integration test which ensures the fallback RPC nodes are working correctly.

Test should:

1. Select all networks both mainnet and testnet
2. open the network status page (Select Active Networks -> 'Node' menu item

There should be no red unhappy faces in the list.

Note that by default, the integration tests are using the Fallback RPC nodes (from ```EthereumNetworkBase```), so no action there is required.