 Returns a (possibly null) reference to a cGroupsHandler. This handler is
   * non-null only if one or more of the known cgroups-based resource
   * handlers are in use and have been initialized.
 Returns a (possibly null) reference to a cGroupsHandler. This handler is
   * non-null only if one or more of the known cgroups-based resource
   * handlers are in use and have been initialized. | ResourceHandlerModule.java