test: fix tls-inception flakiness

cherry-picked the following from master

commit 3b94991
Author: Santiago Gimeno <santiago.gimeno@gmail.com>
Date:   Tue Dec 8 14:57:22 2015 +0100

    test: fix tls-inception flakiness

    When sending a very large buffer (400000 bytes) the test fails due
    to the client socket from the `a` server erroring with `ECONNRESET`.
    There's a race condition between the closing of this socket and the
    `ssl` socket closing on the other side of the connection. To improve
    things, destroy the socket as soon as possible: in the `end` event
    of the `dest` socket.

    PR-URL: nodejs/node#4195
    Reviewed-By: Brian White <mscdex@mscdex.net>
    Reviewed-By: Fedor Indutny <fedor@indutny.com>

test/simple/test-tls-inception.js

@@ -49,6 +49,9 @@ a = tls.createServer(options, function (socket) {
   var dest = net.connect(options);
   dest.pipe(socket);
   socket.pipe(dest);
+  dest.on('end', function() {
+     socket.destroy();
+   });
 });
 
 // the "target" server