test: fix test-http-agent-keepalive again

Roll it back to previous version as the http keepalive sec fix no longer
adds the event listener.

Signed-off-by: Santiago Gimeno <santiago.gimeno@gmail.com>
PR-URL: #488
Reviewed-By: Rafael Gonzaga <rafael.nunu@hotmail.com>

Author: santigimeno

test/addons/nsolid-tracing/test-http-agent-keepalive.js

@@ -279,7 +279,7 @@ setupNSolid(common.mustSucceed(({ addresses }) => {
   function checkListeners(socket) {
     const callback = common.mustCall(() => {
       if (!socket.destroyed) {
-        assert.strictEqual(socket.listenerCount('data'), 1);
+        assert.strictEqual(socket.listenerCount('data'), 0);
         assert.strictEqual(socket.listenerCount('drain'), 0);
         // Sockets have freeSocketErrorListener.
         assert.strictEqual(socket.listenerCount('error'), 1);