MEDIUM: http: Use the new _HA_ATOMIC_* macros.

Use the new _HA_ATOMIC_* macros and add barriers where needed.
diff --git a/src/http_act.c b/src/http_act.c
index 0346be0..c8618ea 100644
--- a/src/http_act.c
+++ b/src/http_act.c
@@ -192,10 +192,10 @@
 	s->req.analysers = 0;
 	s->res.analysers = 0;
 
-	HA_ATOMIC_ADD(&s->be->be_counters.denied_req, 1);
-	HA_ATOMIC_ADD(&sess->fe->fe_counters.denied_req, 1);
+	_HA_ATOMIC_ADD(&s->be->be_counters.denied_req, 1);
+	_HA_ATOMIC_ADD(&sess->fe->fe_counters.denied_req, 1);
 	if (sess->listener && sess->listener->counters)
-		HA_ATOMIC_ADD(&sess->listener->counters->denied_req, 1);
+		_HA_ATOMIC_ADD(&sess->listener->counters->denied_req, 1);
 
 	if (!(s->flags & SF_ERR_MASK))
 		s->flags |= SF_ERR_PRXCOND;