fix(select): allow ngOptions to be set in $timeout

Fix angular 1.3 regression where empty string was shown

Closes #9714
If the expression on line 215 evaluates to true, then we execute the statement:

    this.renderUnknownOption(value);

But, we should only render the unknown option if no option is currently selected. If an option is selected, the select element should only show the values defined in ngOptions.