docs($httpBackend): fix typo/mismatch

There is an mismatch for status in controller and test.
In controller $scope.status = 'ERROR!' and in test we
expect($rootScope.status).toBe('Failed...') so the test will fail;

Closes angular#12834

Author: andriivandakurov

src/ngMock/angular-mocks.js

@@ -1023,7 +1023,7 @@ angular.mock.dump = function(object) {
       $http.post('/add-msg.py', message, { headers: headers } ).success(function(response) {
         $scope.status = '';
       }).error(function() {
-        $scope.status = 'ERROR!';
+        $scope.status = 'Failed...';
       });
     };
   }