http2: allow port 80 in http2.connect

Due to how WHATWG-URL parser works, port numbers are omitted if
they are the default port for a scheme. This meant that
http2.connect could not accept connections on port 80 with http
scheme. Fix this bug by detecting http: scheme and setting port
to 80.

Fixes: nodejs#14304

lib/internal/http2/core.js

@@ -2413,7 +2413,8 @@ function connect(authority, options, listener) {
   debug(`connecting to ${authority}`);
 
   const protocol = authority.protocol || options.protocol || 'https:';
-  const port = '' + (authority.port !== '' ? authority.port : 443);
+  const port = '' + (authority.port !== '' ?
+    authority.port : (authority.protocol === 'http:' ? 80 : 443));
   const host = authority.hostname || authority.host || 'localhost';
 
   let socket;

test/parallel/test-http2-client-port-80.js

@@ -0,0 +1,19 @@
+'use strict';
+
+const common = require('../common');
+if (!common.hasCrypto)
+  common.skip('missing crypto');
+const assert = require('assert');
+const http2 = require('http2');
+const net = require('net');
+
+// Verifies that port 80 gets set as expected
+
+const connect = net.connect;
+net.connect = common.mustCall((...args) => {
+  assert.strictEqual(args[0], '80');
+  return connect(...args);
+});
+
+const client = http2.connect('http://localhost:80');
+client.destroy();