Userland clean up (#1277)

* Improve logging, remove unused CLI and move discovery

* Correct tests

* Handle flag correctly

beacon_node/eth2_libp2p/src/discovery/subnet_predicate.rs

@@ -0,0 +1,33 @@
+///! The subnet predicate used for searching for a particular subnet.
+use super::*;
+
+/// Returns the predicate for a given subnet.
+pub fn subnet_predicate<TSpec>(
+    subnet_id: SubnetId,
+    log: &slog::Logger,
+) -> impl Fn(&Enr) -> bool + Send
+where
+    TSpec: EthSpec,
+{
+    let log_clone = log.clone();
+
+    move |enr: &Enr| {
+        if let Some(bitfield_bytes) = enr.get(BITFIELD_ENR_KEY) {
+            let bitfield = match BitVector::<TSpec::SubnetBitfieldLength>::from_ssz_bytes(
+                bitfield_bytes,
+            ) {
+                Ok(v) => v,
+                Err(e) => {
+                    warn!(log_clone, "Could not decode ENR bitfield for peer"; "peer_id" => format!("{}", enr.peer_id()), "error" => format!("{:?}", e));
+                    return false;
+                }
+            };
+
+            return bitfield.get(*subnet_id as usize).unwrap_or_else(|_| {
+                                   debug!(log_clone, "Peer found but not on desired subnet"; "peer_id" => format!("{}", enr.peer_id()));
+                false
+            });
+        }
+        false
+    }
+}