QOAuth2AuthorizationCodeFlow doesn't handle access token errors

Scenario:

1. Obtain access code.
2. QOAuth2AuthorizationCodeFlow goes to TemporaryCredentialsReceived and requests access token.
3. Access token request results in an error.
4. QOAuth2AuthorizationCodeFlow doesn't reset its state and stays at TemporaryCredentialsReceived - there's no way tell if there was an error or not.