[TIMOB-18709] iOS: Incorrect fallback in Authentication Challenge

It seems like the implementation of the authentication challenge on https://github.com/appcelerator/APSHTTPClient/blob/master/APSHTTPClient/APSHTTPRequest.m is not done properly. Specifically in this part:

if (!handled) {
        if ([challenge.sender respondsToSelector:@selector(performDefaultHandlingForAuthenticationChallenge:)]) {
            [challenge.sender performDefaultHandlingForAuthenticationChallenge:challenge];
        } else {
            [challenge.sender continueWithoutCredentialForAuthenticationChallenge:challenge];
        }
    }

Whenever an error occurs by the validation (for example when the server gives back a wrong certificate), Titanium fallbacks to the standard certificate checks bypassing the desired and given certificate pinning. This bug has successfully reproduced by installing our own CA-certificate in a test device and thus bypassing the check with the certificate of the server and being able to perform a man in the middle attack.