Use the internal port as binding port if available (#162)

src/Microsoft.Tye.Hosting/DockerRunner.cs

@@ -108,7 +108,7 @@ namespace Microsoft.Tye.Hosting
                     status.Ports = ports.Select(p => p.Port);
 
                     // These ports should also be passed in not assuming ASP.NET Core
-                    environment["ASPNETCORE_URLS"] = string.Join(";", ports.Select(p => $"{p.Protocol ?? "http"}://*:{p.Port}"));
+                    environment["ASPNETCORE_URLS"] = string.Join(";", ports.Select(p => $"{p.Protocol ?? "http"}://*:{p.InternalPort ?? p.Port}"));
 
                     portString = string.Join(" ", ports.Select(p => $"-p {p.Port}:{p.InternalPort ?? p.Port}"));