MINOR: http-rules: Use http_reply structure for http return rules

MINOR: http-rules: Use http_reply structure for http return rules

No real change here. Instead of using an internal structure to the action rule,
the http return rules are now stored as an http reply. The main change is about
the action type. It is now always set to ACT_CUSTOM. The http reply type is used
to know how to evaluate the rule.