MINOR: http-rules: Add capture action to http-after-response ruleset

MINOR: http-rules: Add capture action to http-after-response ruleset

It is now possible to perform captures on the response when
http-after-response rules are evaluated. It may be handy to capture headers
from responses generated by HAProxy.

This patch is trivial, it may be backported if necessary.

(cherry picked from commit ba8f06304e538d763a506526a63285c33d26af47)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>