Fix Internetwork defualt case for localhost

If we're AddressFamily.Unspecified, that'll always error. Assume IPv4 (as we did before).

StackExchange.Redis.Tests/ConnectByIP.cs

@@ -14,14 +14,17 @@ public void ParseEndpoints()
             var eps = new EndPointCollection
             {
                 { "127.0.0.1", 1000 },
-                { "::1", 1001 }
+                { "::1", 1001 },
+                { "localhost", 1002 }
             };
 
             Assert.Equal(AddressFamily.InterNetwork, eps[0].AddressFamily);
             Assert.Equal(AddressFamily.InterNetworkV6, eps[1].AddressFamily);
+            Assert.Equal(AddressFamily.Unspecified, eps[2].AddressFamily);
 
             Assert.Equal("127.0.0.1:1000", eps[0].ToString());
             Assert.Equal("[::1]:1001", eps[1].ToString());
+            Assert.Equal("Unspecified/localhost:1002", eps[2].ToString());
         }
 
         [Fact]

StackExchange.Redis.Tests/RealWorld.cs

-using System;
-using System.IO;
-using System.Threading;
+using System.Threading;
 using Xunit;
 using Xunit.Abstractions;
 
 namespace StackExchange.Redis.Tests
 {
-    public class RealWorld
+    public class RealWorld : TestBase
     {
-        public ITestOutputHelper Output { get; }
-        public RealWorld(ITestOutputHelper output) => Output = output;
+        public RealWorld(ITestOutputHelper output) : base(output) { }
 
         [Fact]
         public void WhyDoesThisNotWork()
         {
-            var sw = new StringWriter();
             Output.WriteLine("first:");
-            using (var conn = ConnectionMultiplexer.Connect("localhost:6379,localhost:6380,name=Core (Q&A),tiebreaker=:RedisMaster,abortConnect=False", sw))
+            var config = ConfigurationOptions.Parse("localhost:6379,localhost:6380,name=Core (Q&A),tiebreaker=:RedisMaster,abortConnect=False");
+            Assert.Equal(2, config.EndPoints.Count);
+            Output.WriteLine("Endpoint 0: {0} (AddressFamily: {1})", config.EndPoints[0], config.EndPoints[0].AddressFamily);
+            Output.WriteLine("Endpoint 1: {0} (AddressFamily: {1})", config.EndPoints[1], config.EndPoints[1].AddressFamily);
+
+            using (var conn = ConnectionMultiplexer.Connect("localhost:6379,localhost:6380,name=Core (Q&A),tiebreaker=:RedisMaster,abortConnect=False", Writer))
             {
-                Output.WriteLine(sw.ToString());
                 Output.WriteLine("");
                 Output.WriteLine("pausing...");
                 Thread.Sleep(200);
                 Output.WriteLine("second:");
 
-                sw = new StringWriter();
-                bool result = conn.Configure(sw);
+                bool result = conn.Configure(Writer);
                 Output.WriteLine("Returned: {0}", result);
-                Output.WriteLine(sw.ToString());
             }
         }
     }

StackExchange.Redis/StackExchange/Redis/SocketManager.cs

@@ -141,7 +141,7 @@ public SocketManager(string name, bool useHighPrioritySocketThreads)
             dedicatedWriter.Priority = useHighPrioritySocketThreads ? ThreadPriority.AboveNormal : ThreadPriority.Normal;
 #else
             Thread dedicatedWriter = new Thread(writeAllQueues);
-#endif
+#endif
             dedicatedWriter.Name = name + ":Write";
             dedicatedWriter.IsBackground = true; // should not keep process alive
             dedicatedWriter.Start(this); // will self-exit when disposed
@@ -174,7 +174,8 @@ public void Dispose()
 
         internal SocketToken BeginConnect(EndPoint endpoint, ISocketCallback callback, ConnectionMultiplexer multiplexer, TextWriter log)
         {
-            var socket = new Socket(endpoint.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
+            var addressFamily = endpoint.AddressFamily == AddressFamily.Unspecified ? AddressFamily.InterNetwork : endpoint.AddressFamily;
+            var socket = new Socket(addressFamily, SocketType.Stream, ProtocolType.Tcp);
             SetFastLoopbackOption(socket);
             socket.NoDelay = true;
             try