Add output and retries to AddressRegistrationTests (#57903)

They're among our flakiest kestrel tests and they're already being retried on mac.  Given that the error doesn't seem to be about kestrel's behavior, a retry seems reasonable.

Part of #27377

Author: amcasey

src/Testing/src/HttpClientSlim.cs

@@ -108,11 +108,7 @@ private static async Task<string> ReadResponse(Stream stream)
 
     private static async Task<string> RetryRequest(Func<Task<string>> retryBlock)
     {
-        var retryCount = 1;
-        if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX))
-        {
-            retryCount = 3;
-        }
+        var retryCount = RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? 1 : 3;
 
         for (var retry = 0; retry < retryCount; retry++)
         {
@@ -190,7 +186,12 @@ public static async Task<Socket> GetSocket(Uri requestUri)
 
         if (socket == null)
         {
+#if NETCOREAPP
+            // Include the host and port explicitly in case there's a parsing issue
+            throw new SocketException((int)socketArgs.SocketError, $"Failed to connect to server {requestUri.Host} on port {requestUri.Port}");
+#else
             throw new SocketException((int)socketArgs.SocketError);
+#endif
         }
         else
         {