tests BUGFIX schema dir from the repository must be used

The schemas are not installed yet.
diff --git a/tests/test_server_thread.c b/tests/test_server_thread.c
index 2320b23..c5944ea 100644
--- a/tests/test_server_thread.c
+++ b/tests/test_server_thread.c
@@ -816,6 +816,8 @@
     assert(!ret);
 #endif
 
+    ret = nc_client_schema_searchpath(TESTS_DIR"/../schemas");
+    assert(!ret);
     clients_start_cleanup();
 
     /* threads'n'stuff */
@@ -834,6 +836,7 @@
 
     pthread_barrier_destroy(&barrier);
 
+    nc_client_schema_searchpath(NULL);
     nc_server_destroy();
     ly_ctx_destroy(ctx, NULL);