core: reset ap_runtime_dir to NULL after AP_SQ_MS_DESTROY_CONFIG.
ap_runtime_dir_relative() might reuse ap_runtime_dir from previously cleared
pconf otherwise.
@@ -5846,6 +5846,7 @@ static int core_upgrade_storage(request_rec *r)
static void register_hooks(apr_pool_t *p)
{
+ ap_runtime_dir = NULL;
errorlog_hash = apr_hash_make(p);
ap_register_log_hooks(p);
ap_register_config_hooks(p);
