Do thread cleanup within the same thread context.

test/helpers/test_utils.h

@@ -0,0 +1,21 @@
+#ifndef LIBTORRENT_TEST_UTILS_H
+#define LIBTORRENT_TEST_UTILS_H
+
+#include <functional>
+#include <unistd.h>
+
+inline bool
+wait_for_true(std::function<bool ()> test_function) {
+  int i = 100;
+
+  do {
+    if (test_function())
+      return true;
+
+    usleep(10 * 1000);
+  } while (--i);
+
+  return false;
+}
+
+#endif // LIBTORRENT_TEST_UTILS_H