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

This reverts commit dc149de.

This commit fixes a bug caused by Firefox updating `select.value` on hover. However, it
causes other bugs with select including the issue described in angular#7715. This issue causes
selects with a blank disabled option to skip to the second option. We filed a bug
with Firefox for the problematic behavior this commit addresses
https://bugzilla.mozilla.org/show_bug.cgi?id=1039047, and alternate Angular fixes are being
investigated. The test introduced in this commit does test a valid case and is therefore not
reverted.

Author: Erin Altenhof-Long

src/ng/directive/select.js

@@ -394,12 +394,6 @@ 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);
           });
@@ -537,7 +531,7 @@ 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));
                 }
               } else {