MINOR: counters: make it easier to extend the amount of tracked counters

By properly affecting the flags and values, it becomes easier to add
more tracked counters, for example for experimentation. It also slightly
reduces the code and the number of tests. No counters were added with
this patch.
diff --git a/include/proto/session.h b/include/proto/session.h
index 3b6e1fc..5188639 100644
--- a/include/proto/session.h
+++ b/include/proto/session.h
@@ -80,19 +80,16 @@
 	void *ptr;
 	int i;
 
-	if (!(s->flags & (SN_BE_TRACK_SC1|SN_BE_TRACK_SC2)))
+	if (likely(!(s->flags & SN_BE_TRACK_ANY)))
 		return;
 
 	for (i = 0; i < sizeof(s->stkctr) / sizeof(s->stkctr[0]); i++) {
 		if (!s->stkctr[i].entry)
 			continue;
 
-		if ((i == 0) && !(s->flags & SN_BE_TRACK_SC1))
+		if (!(s->flags & (SN_BE_TRACK_SC1 << i)))
 			continue;
 
-		if ((i == 1) && !(s->flags & SN_BE_TRACK_SC2))
-			continue;
-
 		ptr = stktable_data_ptr(s->stkctr[i].table, s->stkctr[i].entry, STKTABLE_DT_CONN_CUR);
 		if (ptr)
 			stktable_data_cast(ptr, conn_cur)--;
@@ -100,7 +97,7 @@
 		stksess_kill_if_expired(s->stkctr[i].table, s->stkctr[i].entry);
 		s->stkctr[i].entry = NULL;
 	}
-	s->flags &= ~(SN_BE_TRACK_SC1|SN_BE_TRACK_SC2);
+	s->flags &= ~SN_BE_TRACK_ANY;
 }
 
 /* Increase total and concurrent connection count for stick entry <ts> of table
@@ -169,17 +166,14 @@
 	void *ptr;
 	int i;
 
-	if (likely(!(s->flags & (SN_BE_TRACK_SC1|SN_BE_TRACK_SC2))))
+	if (likely(!(s->flags & SN_BE_TRACK_ANY)))
 		return;
 
 	for (i = 0; i < sizeof(s->stkctr) / sizeof(s->stkctr[0]); i++) {
 		if (!s->stkctr[i].entry)
 			continue;
 
-		if ((i == 0) && !(s->flags & SN_BE_TRACK_SC1))
-			continue;
-
-		if ((i == 1) && !(s->flags & SN_BE_TRACK_SC2))
+		if (!(s->flags & (SN_BE_TRACK_SC1 << i)))
 			continue;
 
 		ptr = stktable_data_ptr(s->stkctr[i].table, s->stkctr[i].entry, STKTABLE_DT_HTTP_REQ_CNT);