ngModelWatch breaks if $modelValue is object

[serzh]

When using ngModel inside custom directive there is a chance to break ngModelWatch fn. On the first run ngModelWatch will set $modelValue to ngModelGet($scope). Then, if you change property of that scope var (ngModelGet($scope)) it will change the properties on the $modelValue, because it is the same object! So if you have some $formatters they won't be called at all.

Here is plnkr for demonstration.

[Narretz]

Duplicate of #5449