benchmark: fix chunky client benchmark execution
This commit fixes a few things for this benchmark:
- Ensures the temporary directory for the unix socket exists.
- Prevents the client code from being run directly because the server script is the one that calls out the client code. This is done by simply renaming the client script.
- Ensures the server is closed once the client benchmarks have finished.
- Since this is an http benchmark, it should be moved to the http benchmarks subdirectory.