Nested rfactor fix, update predicates as well as source. (#3382)

* Nested rfactor fix, update predicates as well as source.

* Linter

* Syntax fix.

src/schedule/schedule_dataflow_rewrite.cc

@@ -761,12 +761,15 @@ Array<Tensor> Schedule::rfactor(const Tensor& tensor,
   VarReplacer replacer(vsub);
   Array<Expr> new_source = ir::UpdateArray(reduce->source,
     [&replacer] (const Expr& e) { return replacer.Mutate(e); });
+
+  Expr new_pred = replacer.Mutate(predicate);
+
   std::vector<Expr> body;
   for (size_t idx = 0; idx < reduce->source.size(); ++idx) {
     body.emplace_back(Reduce::make(reduce->combiner,
                                    new_source,
                                    n->reduce_axis,
-                                   predicate,
+                                   new_pred,
                                    idx));
   }
   n->body = Array<Expr>(body);