code: public <T extends JobProperty> T getProperty(Class<T> clazz) {
          if (clazz == BuildDiscarderProperty.class && logRotator != null) {
              return clazz.cast(new BuildDiscarderProperty(logRotator));
          }
          return _getProperty(clazz);
      }
docs: Gets the specific property, or null if the property is not configured for
  this job.