fix(Controller): Errors are hidden by default

[jokemanfire]

I don't think errors should be hidden here, it will cause the error to occur in the subsequent process, and I think this design is incorrect.
you can choose to ignore this error ,but should not hide it in inner.

  let cg = Cgroup::new(hierarchies::auto(), path).unwrap();
  let mem_controller: &MemController = cg.controller_of().unwrap();
  mem_controller.set_limit(10 * 1024 * 1024).unwrap(); // 10M

this will case the panic occur in set_limit,this is unreasonable.