fix scope tracking when converting loops

src/compiler/transformers/es6.ts

@@ -1796,7 +1796,7 @@ namespace ts {
                 }
             }
 
-            let loopBody = visitEachChild(node.statement, visitor, context);
+            let loopBody = visitNode(node.statement, visitor, isStatement);
 
             const currentState = convertedLoopState;
             convertedLoopState = outerConvertedLoopState;

tests/baselines/reference/nestedBlockScopedBindings13.js

@@ -10,7 +10,7 @@ for (; false;) {
 }
 
 //// [nestedBlockScopedBindings13.js]
-var _loop_1 = function() {
+var _loop_1 = function () {
     var x;
     (function () { return x; });
 };