Multiple problems with $validate after a validator changes #7836

See example at: http://plnkr.co/edit/i320YT1EX8Dmst6m7dVM?p=preview

1. value always becomes valid if $validate is invoked while the value is invalid: enter max=5, value=123456 => change max to be 3 => value is now valid.
2. model remains undefined even after $validate validators are now valid: enter max=5, value=123456 => change max to be 9 => value is still undefined.
3. model does not become undefined even after $validate validators are now invalid: max=9, value=123456 => change max to be 5 => value is still 123456