test: use invalid host according to RFC2606

Refs: nodejs#14781
Refs: https://tools.ietf.org/html/rfc2606#section-2

Author: tniessen

test/parallel/test-http-client-req-error-dont-double-fire.js

@@ -3,8 +3,8 @@ const assert = require('assert');
 const http = require('http');
 const common = require('../common');
 
-// not exists host
-const host = '*'.repeat(256);
+// Invalid hostname as per https://tools.ietf.org/html/rfc2606#section-2
+const host = 'this.hostname.is.invalid';
 const req = http.get({ host });
 const err = new Error('mock unexpected code error');
 req.on('error', common.mustCall(() => {