MINOR: http-rules: Add a flag on redirect rules to know the rule direction

MINOR: http-rules: Add a flag on redirect rules to know the rule direction

HTTP redirect rules can be evaluated on the request or the response path. So
when a redirect rule is evaluated, it is important to have this information
because some specific processing may be performed depending on the direction. So
the REDIRECT_FLAG_FROM_REQ flag has been added. It is set when applicable on the
redirect rule during the parsing.

This patch is mandatory to fix a bug on redirect rule. It must be backported to
all stable versions.