Fix race condition in poll_for_response

Expands on !34 (closed)

@fziglio - this is your patch but during reviewing I wanted to add comments, so that's what I did :) Which then lead to some restructuring. I left the steps in place so you can follow my thoughts, I haven't tested it yet though.

Funnily enough, the diff against master is very easy to review too because it's just one hunk that gets added.