Better handle waiting Auth data

[abs0]

To try to better handle the following case

• App starts, triggers OAuth2 on connected phone
• User takes a while to login to TrainAsONE and click grant, so the app times out, garmin connect saves access code
• User starts app again, we do not have a code so we trigger OAuth2 again
• garmin connect return access code immediately registerForOAuthMessages is called, but we start OAuth2 process anyway
• user sees the authorisation dialog a second time, even though they completed it last time, and clicking cancel will continue the app fine