Do not populate DrupalApcCache::$operations when $conf['apc_show_debug'] has not been set or it is FALSE

DrupalApcCache::$operations the list of the operations done on the cache, and it is populated even when $conf['apc_show_debug'] has not been set or it is set to FALSE.
Since the content of DrupalApcCache::$operations is shown only when $conf['apc_show_debug'] is set to TRUE, that should be the only case when DrupalApcCache::$operations gets populated. Otherwise, in a production server, the module would waste memory for no reason. (This is why I consider this a bug.)