[BUG][CCI] Fixed typo in connection _agent

[Naurabay]

What is the bug?

The declared variable _agent is local in the interface of the Connection class, here:

\\Connection.d.ts
export default class Connection {
...
  _agent: http.Agent | https.Agent | hpagent.HttpProxyAgent | hpagent.HttpsProxyAgent;
...

The gist of the bug is that, it was discovered that in the class itself, the call goes to the agent variable, example:

if (typeof opts.agent === 'function') {
      this.agent = opts.agent(opts);
    } else if (opts.agent === false) {
      this.agent = undefined;
    }

Should be

if (typeof opts.agent === 'function') {
      this._agent = opts.agent(opts);
    } else if (opts.agent === false) {
      this.a_gent = undefined;
    }

[nhtruong]

Nice Catch!