Avoid an unnecessary closure allocation in ListenerSecondary (#1485)

The tcs is being passed as the state, so use it from the state instead
of closing over it.

Author: justinvp

src/Microsoft.AspNetCore.Server.Kestrel/Internal/Http/ListenerSecondary.cs

@@ -109,13 +109,14 @@ private void ConnectedCallback(UvConnectRequest connect, int status, Exception e
                     {
                         req.Dispose();
 
+                        var innerTcs = (TaskCompletionSource<int>)state;
                         if (ex != null)
                         {
-                            tcs.SetException(ex);
+                            innerTcs.SetException(ex);
                         }
                         else
                         {
-                            tcs.SetResult(0);
+                            innerTcs.SetResult(0);
                         }
                     },
                     tcs);