BUG: MAJOR: lb_map: server map calculation broken

Adrian Williams reported that several balancing methods were broken and
sent all requests to one backend. This is a regression in haproxy 1.8 where
the server score was not correctly recalculated.

This fix must be backported to the 1.8 branch.

src/lb_map.c

@@ -122,7 +122,7 @@ void recalc_server_map(struct proxy *px)
 			}
 		}
 		px->lbprm.map.srv[o] = best;
-		HA_ATOMIC_ADD(&best->wscore, tot);
+		HA_ATOMIC_SUB(&best->wscore, tot);
 	}
 }