Revert "BUG/MEDIUM: lua: can't handle the response bytes"

Revert "BUG/MEDIUM: lua: can't handle the response bytes"

This reverts commit cd9084f77683106ace2fb863080e7d10e71c39fc.

This commit introduced a regression making it impossible to leave
process_session() during a forced yield because the analyser was always
set on the response even if not needed. The result was a busy loop
making haproxy spin at 100% without even polling anymore in case a
forced yield was performed.

The problem it tried to address (intercept response data from a request
analyser before forwarding) is not a trivial issue to address since
wakeups based on reads will not necessarily happen unless there's write
activity.

Anyway, if functions are attached specifically to a request or to a
response, it's for a reason. So for now let's be clear about the fact
that it's unreliable to try to process data from the opposite channel
until a better solution is found.