Don't allow setting user/team/passkey on a machine which is synched to an account.

[jcoffland]

The current situation causes confusion. If you're not logged in you can set user/team/passkey via machine settings but this only affects the machine temporarily. Once it resyncs with the account the changes are reverted.

Web Control can detect if the machine is synched to an account even if Web Control is not logged in. In this case it should prevent setting user/team/passkey and direct the user to login and use the account settings.