Will be nice to clear auth credentials. For example, I'm using a proxy that accepts options via username:

```
proxy.com:8080
user: wiliam_country_US
```

So, if I want to change the peer node, I change my username:

```
proxy.com:8080
user: wiliam_country_GB
```

But, I'm not changing the proxy, so electron has valid credentials and is not going to trigger `login` event.

I'm searching the way to clean auth settings so electron asks them again.
atom/browser/net/atom_url_request.cc
DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
  if (request_) {
    request_->Cancel();
  }
  DoTerminate();
}
void AtomURLRequest::DoSetExtraHeader(const std::string& name,
                                      const std::string& value) const {
  DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
  if (!request_) {
    return;
  }
  request_->SetExtraRequestHeaderByName(name, value, true);
}
void AtomURLRequest::DoRemoveExtraHeader(const std::string& name) const {
  DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
  if (!request_) {
    return;
  }
  request_->RemoveRequestHeaderByName(name);
}
void AtomURLRequest::DoSetAuth(const base::string16& username,
                               const base::string16& password) const {
  DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
  if (!request_) {
    return;
  }
  request_->SetAuth(net::AuthCredentials(username, password));
}
void AtomURLRequest::DoCancelAuth() const {