BUG/MINOR: http_act: don't check capture id in backend (2)

BUG/MINOR: http_act: don't check capture id in backend (2)

Please refer to commit 19a69b3740702ce5503a063e9dfbcea5b9187d27 for all the
details. This follow up commit fixes the `http-response capture` case, the
previous one only fixed the `http-request capture` one. The documentation was
already updated and the change to `check_http_res_capture` is identical to
the `check_http_req_capture` change.

This patch must be backported together with 19a69b3740702ce5503a063e9dfbcea5b9187d27.
Most likely this is 1.6+.