Fix shutdown hang on http_client test

diff --git a/test/cutest/include/cut_http_server.h b/test/cutest/include/cut_http_server.h
index 45a01c2..1466ae4 100644
--- a/test/cutest/include/cut_http_server.h
+++ b/test/cutest/include/cut_http_server.h
@@ -197,6 +197,7 @@
     thread_http_server = axutil_thread_create(env->allocator, NULL, http_server, NULL);
     EXPECT_NE(thread_http_server, nullptr);
     if (!thread_http_server) return -1;
+    axutil_thread_detach(thread_http_server);
     AXIS2_SLEEP(2);
 	return 0;
 }