tests: fix test failures with node v19 change to default http clients…

… to use keep-alive (#2803)

As of nodejs/node#37184 node v19 and later
defaults the http,https.globalAgent to use keep-alive:

  - globalAgent: new Agent()
  + globalAgent: new Agent({ keepAlive: true, scheduling: 'lifo', timeout: 5000 })

This change in default broke a couple tests. The agent itself is
unaffected because our http client already uses a custom http agent
using keep-alive.

test/instrumentation/modules/http2.test.js

@@ -455,6 +455,7 @@ test('handling HTTP/1.1 request to http2.createSecureServer with allowHTTP1:true
 
     // Make an HTTP/1.1 request.
     var getOpts = {
+      agent: new https.Agent(),
       protocol: 'https:',
       host: 'localhost',
       port: port,

test/parsers.test.js

@@ -239,6 +239,7 @@ function onRequest (cb) {
 
   server.listen(function () {
     var opts = {
+      agent: new http.Agent(),
       port: server.address().port
     }
     var req = http.request(opts, function (res) {