test: fix luacheck warnings in test/xlog-py

Closes #5469

Reviewed-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Reviewed-by: Igor Munkin <imun@tarantool.org>

Co-authored-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Co-authored-by: Igor Munkin <imun@tarantool.org>

.luacheckrc

@@ -47,7 +47,6 @@ exclude_files = {
     "test/vinyl/**/*.lua",
     "test/wal_off/**/*.lua",
     "test/xlog/*.test.lua",
-    "test/xlog-py/**/*.lua",
     "third_party/**/*.lua",
     ".rocks/**/*.lua",
     ".git/**/*.lua",

test/xlog-py/box.lua

 #!/usr/bin/env tarantool
-os = require('os')
+local os = require('os')
 
 box.cfg{
     listen              = os.getenv("LISTEN"),