Cannot access install.ps1 when accessing through a forwarded port

[jborean93]

When the Chocolatey server host is sitting behind a forwarded port, it may fail to access the install.ps1 script. When turning on more logging you would see the following error

<Error><Message>An error has occurred.</Message><ExceptionMessage>Unable to connect to the remote server</ExceptionMessage><ExceptionType>System.Net.WebException</ExceptionType><StackTrace>   at System.Net.WebClient.DownloadDataInternal(Uri address, WebRequest& request)
   at System.Net.WebClient.DownloadString(Uri address)
   at System.Net.WebClient.DownloadString(String address)
   at SimpleChocolateyServer.Contollers.InstallController.DownloadPowerShellInstallScript()
   at lambda_method(Closure , Object , Object[] )
   at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ActionExecutor.<>c__DisplayClass10.<GetExecutor>b__9(Object instance, Object[] methodParameters)
   at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ActionExecutor.Execute(Object instance, Object[] arguments)
   at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ExecuteAsync(HttpControllerContext controllerContext, IDictionary`2 arguments, CancellationToken cancellationToken)
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Controllers.ApiControllerActionInvoker.<InvokeActionAsyncCore>d__0.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Controllers.ActionFilterResult.<ExecuteAsync>d__2.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Dispatcher.HttpControllerDispatcher.<SendAsync>d__1.MoveNext()</StackTrace><InnerException><Message>An error has occurred.</Message><ExceptionMessage>No connection could be made because the target machine actively refused it 127.0.0.1:8080</ExceptionMessage><ExceptionType>System.Net.Sockets.SocketException</ExceptionType><StackTrace>   at System.Net.Sockets.Socket.DoConnect(EndPoint endPointSnapshot, SocketAddress socketAddress)
   at System.Net.ServicePoint.ConnectSocketInternal(Boolean connectFailure, Socket s4, Socket s6, Socket& socket, IPAddress& address, ConnectSocketState state, IAsyncResult asyncResult, Exception& exception)</StackTrace></InnerException></Error>

This is due to the code at https://github.com/chocolatey/simple-server/blob/master/src/SimpleChocolateyServer/Controllers/InstallController.cs#L44 where the IIS service tries to access itself using the URL the client used. In the case of a forwarded port, this may not be a valid URL service side.

A simple example of this is if Choco server is on a Virtualbox where port 80 is forwarded to port 8080 on the VB host. I would access the Chocolatey URL with http://127.0.0.1:8080/install.ps1 and the code would then try and access http://127.0.0.1:8080/chocolatey/Packages()?$filter=((Id%20eq%20%27chocolatey%27)%20and%20(not%20IsPrerelease))%20and%20IsLatestVersion which may not be valid on that actual host. This is a pretty niche case but I thought it best to add an issue about it.