Change BootNode to use Discv5 instead of Kademlia (#3203)

* add new test

* specify ecdsa keygen

* skip test

* fix ref

* comment again

* fix test and clean up

* gaz

* change to another format

* Apply suggestions from code review

Co-Authored-By: Preston Van Loon <preston@prysmaticlabs.com>

* fix docker build

* add close

tools/bootnode/bootnode_test.go

@@ -0,0 +1,55 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/ethereum/go-ethereum/p2p/discv5"
+	"github.com/prysmaticlabs/prysm/shared/iputils"
+	_ "go.uber.org/automaxprocs"
+)
+
+func TestBootnode_OK(t *testing.T) {
+	ipAddr, err := iputils.ExternalIPv4()
+	if err != nil {
+		t.Fatal(err)
+	}
+	privKey := extractPrivateKey()
+	listener := createListener(ipAddr, 4000, privKey)
+	defer listener.Close()
+
+	privKey = extractPrivateKey()
+	listener2 := createListener(ipAddr, 4001, privKey)
+	defer listener.Close()
+
+	err = listener.SetFallbackNodes([]*discv5.Node{listener2.Self()})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = listener2.SetFallbackNodes([]*discv5.Node{listener.Self()})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// test that both the nodes have the other peer stored in their local table.
+	listenerNode := listener.Self()
+	listenerNode2 := listener2.Self()
+
+	nodes := listener.Lookup(listenerNode2.ID)
+	if len(nodes) != 2 {
+		t.Errorf("Length of nodes stored in table is not expected. Wanted %d but got %d", 2, len(nodes))
+
+	}
+	if nodes[0].ID != listenerNode2.ID {
+		t.Errorf("Wanted node ID of %s but got %s", listenerNode2.ID, nodes[1].ID)
+	}
+
+	nodes = listener2.Lookup(listenerNode.ID)
+	if len(nodes) != 2 {
+		t.Errorf("Length of nodes stored in table is not expected. Wanted %d but got %d", 2, len(nodes))
+
+	}
+	if nodes[0].ID != listenerNode.ID {
+		t.Errorf("Wanted node ID of %s but got %s", listenerNode.ID, nodes[1].ID)
+	}
+}