tests: internal: upstream: use flb_pthread.h
#include <fluent-bit/flb_config.h>
#include <fluent-bit/flb_upstream.h>
#include <fluent-bit/flb_http_client.h>
+#include <fluent-bit/flb_pthread.h>
#include <monkey/mk_lib.h>
-#include <pthread.h>
#include <time.h>
#include "flb_tests_internal.h"
