http: add default argument for Agent.prototype.getName

PR-URL: https://github.com/nodejs/node/pull/41906
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Ricky Zhou <0x19951125@gmail.com>
Reviewed-By: Mestery <mestery@protonmail.com>

lib/_http_agent.js

@@ -217,7 +217,7 @@ Agent.defaultMaxSockets = Infinity;
 Agent.prototype.createConnection = net.createConnection;
 
 // Get the key for a given set of request options
-Agent.prototype.getName = function getName(options) {
+Agent.prototype.getName = function getName(options = {}) {
   let name = options.host || 'localhost';
 
   name += ':';