Tests: Fix discovery test indcludes on OpenBSD

tests/server/check_discovery.c

@@ -10,6 +10,9 @@
 #include "thread_wrapper.h"
 
 #include <fcntl.h>
+#ifndef WIN32
+#include <sys/stat.h>
+#endif
 #include <check.h>
 
 #ifndef _WIN32