[MINOR] no fixed ports in tests (#340)

* [MINOR] no fixed ports in tests

First enable "0" port in PeerDiscoveryAgent so it binds to
an open port.  Then change the test to use two PeerDiscoveryAgents

The change to zero is accomplished by populating the endpoint with
the actual bound socket instead of the value passed in.  If it is
zero the value will change otherwise it will be the value passed in.

ethereum/p2p/src/main/java/tech/pegasys/pantheon/ethereum/p2p/discovery/PeerDiscoveryAgent.java

@@ -171,7 +171,7 @@ public class PeerDiscoveryAgent implements DisconnectCallback {
                   completion.completeExceptionally(cause);
                   return;
                 }
-                initialize(res.result(), tcpPort);
+                initialize(res.result(), res.result().localAddress().port());
                 this.isActive = true;
                 completion.complete(null);
               });

ethereum/p2p/src/test/java/tech/pegasys/pantheon/ethereum/p2p/discovery/PeerDiscoveryAgentTest.java

@@ -14,7 +14,6 @@ package tech.pegasys.pantheon.ethereum.p2p.discovery;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.awaitility.Awaitility.await;
-import static tech.pegasys.pantheon.util.bytes.BytesValue.fromHexString;
 
 import tech.pegasys.pantheon.crypto.SECP256K1;
 import tech.pegasys.pantheon.ethereum.p2p.api.MessageData;
@@ -130,29 +129,37 @@ public class PeerDiscoveryAgentTest extends AbstractPeerDiscoveryTest {
   @Test
   public void shouldEvictPeerOnDisconnect() {
     final Vertx vertx = Vertx.vertx();
-    final SECP256K1.KeyPair keyPair = SECP256K1.KeyPair.generate();
-    final BytesValue id =
-        fromHexString(
-            "c7849b663d12a2b5bf05b1ebf5810364f4870d5f1053fbd7500d38bc54c705b453d7511ca8a4a86003d34d4c8ee0bbfcd387aa724f5b240b3ab4bbb994a1e09b");
 
-    final DefaultPeer peer = new DiscoveryPeer(id, "127.0.0.1", 30303);
+    final SECP256K1.KeyPair keyPair1 = SECP256K1.KeyPair.generate();
-    final PeerDiscoveryAgent peerDiscoveryAgent =
+    final PeerDiscoveryAgent peerDiscoveryAgent1 =
         new PeerDiscoveryAgent(
             vertx,
-            keyPair,
+            keyPair1,
+            DiscoveryConfiguration.create().setBindHost("127.0.0.1").setBindPort(0),
+            () -> true,
+            new PeerBlacklist());
+    peerDiscoveryAgent1.start(0).join();
+    final DefaultPeer peer = peerDiscoveryAgent1.getAdvertisedPeer();
+
+    final SECP256K1.KeyPair keyPair2 = SECP256K1.KeyPair.generate();
+    final PeerDiscoveryAgent peerDiscoveryAgent2 =
+        new PeerDiscoveryAgent(
+            vertx,
+            keyPair2,
             DiscoveryConfiguration.create()
                 .setBindHost("127.0.0.1")
+                .setBindPort(0)
                 .setBootstrapPeers(Lists.newArrayList(peer)),
             () -> true,
             new PeerBlacklist());
-    peerDiscoveryAgent.start(30303).join();
+    peerDiscoveryAgent2.start(0).join();
 
-    assertThat(peerDiscoveryAgent.getPeers().size()).isEqualTo(1);
+    assertThat(peerDiscoveryAgent2.getPeers().size()).isEqualTo(1);
 
-    final PeerConnection peerConnection = createAnonymousPeerConnection(id);
+    final PeerConnection peerConnection = createAnonymousPeerConnection(peer.getId());
-    peerDiscoveryAgent.onDisconnect(peerConnection, DisconnectReason.REQUESTED, true);
+    peerDiscoveryAgent2.onDisconnect(peerConnection, DisconnectReason.REQUESTED, true);
 
-    assertThat(peerDiscoveryAgent.getPeers().size()).isEqualTo(0);
+    assertThat(peerDiscoveryAgent2.getPeers().size()).isEqualTo(0);
   }
 
   @Test