fix(ngMocks): $logProvider#debugEnabled should work the same within tests

angular.mocks.$LogProvider $logProvider.debugEnabled(false) is crashing
with undefined when run inside karma/jasmine test runner

The following crashes when run inside Karma/Jasmine test suite

```javascript
angular.module('foo', [])
  .config(['$logProvider', function ($logProvider) {
    $logProvider.debugEnabled(false);
  }]);
```

Closes #3612