revert(select): avoid checking option element selected properties in render

This reverts commit dc149de. That commit fixes a bug caused by
Firefox updating `select.value` on hover. However, it
causes other bugs with select including the issue described in #7715. This issue details how
selects with a blank disabled option skip to the second option. We filed a bug
with Firefox for the problematic behavior the reverted commit addresses
https://bugzilla.mozilla.org/show_bug.cgi?id=1039047, and alternate Angular fixes are being
investigated.

Closes #7715 #7855

Author: Erin Altenhof-Long

src/ng/directive/select.js

@@ -395,12 +395,6 @@ var selectDirective = ['$compile', '$parse', function($compile,   $parse) {
                   value = valueFn(scope, locals);
                 }
               }
-              // Update the null option's selected property here so $render cleans it up correctly
-              if (optionGroupsCache[0].length > 1) {
-                if (optionGroupsCache[0][1].id !== key) {
-                  optionGroupsCache[0][1].selected = false;
-                }
-              }
             }
             ctrl.$setViewValue(value);
           });
@@ -538,7 +532,7 @@ var selectDirective = ['$compile', '$parse', function($compile,   $parse) {
                   lastElement.val(existingOption.id = option.id);
                 }
                 // lastElement.prop('selected') provided by jQuery has side-effects
-                if (existingOption.selected !== option.selected) {
+                if (lastElement[0].selected !== option.selected) {
                   lastElement.prop('selected', (existingOption.selected = option.selected));
                   if (msie) {
                     // See #7692

test/ng/directive/selectSpec.js

@@ -733,27 +733,6 @@ describe('select', function() {
       expect(sortedHtml(options[2])).toEqual('<option value="1">3</option>');
     });
 
-    it('should not update selected property of an option element on digest with no change event',
-        function() {
-      createSingleSelect();
-
-      scope.$apply(function() {
-        scope.values = [{name: 'A'}, {name: 'B'}, {name: 'C'}];
-        scope.selected = scope.values[0];
-      });
-
-      var options = element.find('option');
-      var optionToSelect = options.eq(1);
-
-      expect(optionToSelect.text()).toBe('B');
-
-      optionToSelect.prop('selected', true);
-      scope.$digest();
-
-      expect(optionToSelect.prop('selected')).toBe(true);
-      expect(scope.selected).toBe(scope.values[0]);
-    });
-
     describe('binding', function() {
 
       it('should bind to scope value', function() {