message: [libra-node][easy] refactor of loop
  refactored a `for i=0..X.len()`
  into a `for el in X.iter_mut()`
  Closes:
  Approved by: mimoo
diff: @@ -190,26 +190,21 @@ pub fn setup_environment(node_config: &mut NodeConfig) -> LibraHandle {
  validator_network_provider = Some((network.peer_id, runtime, network_builder));
  }
  - for i in 0..node_config.full_node_networks.len() {
  + for mut full_node_network in node_config.full_node_networks.iter_mut() {
  let (runtime, mut network_builder) =
  - setup_network(&mut node_config.full_node_networks[i], RoleType::FullNode);
  + setup_network(&mut full_node_network, RoleType::FullNode);
  +
  + network_runtimes.push(runtime);
  state_sync_network_handles.push(state_synchronizer::network::add_to_network(
  &mut network_builder,
  ));
  -
  let (mempool_sender, mempool_events) =
  libra_mempool::network::add_to_network(&mut network_builder);
  - mempool_network_handles.push((
  - node_config.full_node_networks[i].peer_id,
  - mempool_sender,
  - mempool_events,
  - ));
  + mempool_network_handles.push((full_node_network.peer_id, mempool_sender, mempool_events));
  - let network = &node_config.full_node_networks[i];
  // Start the network provider.
  let _listen_addr = network_builder.build();
  - network_runtimes.push(runtime);
  - debug!("Network started for peer_id: {}", network.peer_id);
  + debug!("Network started for peer_id: {}", full_node_network.peer_id);
  }
  let debug_if = setup_debug_interface(&node_config);
  