QtIFW

Make usage of authorization fallback optional

Asking users to use the authorization fallback in case of authorization errors
might be a bit problematic in some cases. If the users are not familiar with the
concept, running: "<installer_exe> --startserver PRODUCTION,{GUID},{GUID}" from
command line might be confusing or difficult. Also it might not help at all.

So let's make this optional. If the config variable DisableAuthorizationFallback
is set to true the installer will not ask users to run the authorization
fallback but instead it will abort the installation immediately.

In RemoteClient this is implemented by adding a new function called
setAuthorizationFallbackDisabled. The init function could be also extend for
this but the config settings are not loaded at the time when the function is
called.

Change-Id: I4baf1dea34c5cc0016e98df47a9492ee1418c5ee
Reviewed-by: Katja Marttila <katja.marttila@qt.io>
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>