Add a flag to disable peer scoring (#4135)

## Issue Addressed

N/A

## Proposed Changes

Adds a flag for disabling peer scoring. This is useful for local testing and testing small networks for new features.

beacon_node/src/cli.rs

@@ -233,6 +233,14 @@ pub fn cli_app<'a, 'b>() -> App<'a, 'b> {
                 .help("Disables the discv5 discovery protocol. The node will not search for new peers or participate in the discovery protocol.")
                 .takes_value(false),
         )
+        .arg(
+            Arg::with_name("disable-peer-scoring")
+                .long("disable-peer-scoring")
+                .help("Disables peer scoring in lighthouse. WARNING: This is a dev only flag is only meant to be used in local testing scenarios \
+                        Using this flag on a real network may cause your node to become eclipsed and see a different view of the network")
+                .takes_value(false)
+                .hidden(true),
+        )
         .arg(
             Arg::with_name("trusted-peers")
                 .long("trusted-peers")