fix(select): force visual update in IE

IE9, IE10 and IE11 would always show the first <option> as
selected when the user moves from a null <option>
to a non-null one in a non-null <select>.
Even though the model was being updated correctly,
visually, the first <option> always appeared selected.

Setting the `selected` property twice in a row
seems to fix it in all the three versions mentioned above.

Closes #7692
Closes #8158

src/ng/directive/select.js

@@ -546,6 +546,12 @@ var selectDirective = ['$compile', '$parse', function($compile,   $parse) {
                 // lastElement.prop('selected') provided by jQuery has side-effects
                 if (existingOption.selected !== option.selected) {
                   lastElement.prop('selected', (existingOption.selected = option.selected));
+                  if (msie) {
+                    // See #7692
+                    // The selected item wouldn't visually update on IE without this.
+                    // Tested on Win7: IE9, IE10 and IE11. Future IEs should be tested as well
+                    lastElement.prop('selected', existingOption.selected);
+                  }
                 }
               } else {
                 // grow elements