CLEANUP: http: homogenize processing of denied req counter

CLEANUP: http: homogenize processing of denied req counter

The reqdeny/reqideny and reqtarpit/reqitarpit rules used to maintain
the stats counters themselves while http-request deny/tarpit and
rspdeny/rspideny used to centralize them at the point where the
error is processed.

Thus, let's do the same for reqdeny/reqtarpit so that the functions
which iterate over the rules do not have to deal with these counters
anymore.