BUG/MINOR: http-rules: Preserve FLT_END analyzers on reject action

When at least a filter is attached to a stream, FLT_END analyzers must be
preserved on request and response channels.

This patch should be backported as far as 1.8.
diff --git a/src/http_act.c b/src/http_act.c
index b44130a..7b14afd 100644
--- a/src/http_act.c
+++ b/src/http_act.c
@@ -369,8 +369,8 @@
 	si_must_kill_conn(chn_prod(&s->req));
 	channel_abort(&s->req);
 	channel_abort(&s->res);
-	s->req.analysers = 0;
-	s->res.analysers = 0;
+	s->req.analysers &= AN_RES_FLT_END;
+	s->res.analysers &= AN_REQ_FLT_END;
 
 	_HA_ATOMIC_ADD(&s->be->be_counters.denied_req, 1);
 	_HA_ATOMIC_ADD(&sess->fe->fe_counters.denied_req, 1);