Don't visit siblings of the coroutine when looking for yields

When visiting the yields, the root is the stateNode of the coroutine. If
its return value is wrong we'll end up at the alternate of the
workInProgress which will start scanning its children which is wrong.

Author: sebmarkbage

src/renderers/shared/fiber/ReactFiberCompleteWork.js

@@ -85,6 +85,9 @@ module.exports = function<T, P, I, TI, PI, C, CX, PL>(
 
   function appendAllYields(yields : Array<mixed>, workInProgress : Fiber) {
     let node = workInProgress.stateNode;
+    if (node) {
+      node.return = workInProgress;
+    }
     while (node) {
       if (node.tag === HostComponent || node.tag === HostText ||
           node.tag === HostPortal) {
@@ -96,9 +99,6 @@ module.exports = function<T, P, I, TI, PI, C, CX, PL>(
         node = node.child;
         continue;
       }
-      if (node === workInProgress) {
-        return;
-      }
       while (!node.sibling) {
         if (!node.return || node.return === workInProgress) {
           return;