Avoid cleaning up ReactRootView content when reactContext is destroyed

Summary: This diff avoids deleting all the views of ReactRootView when the ReactContext is destroyed (ONLY FOR FABRIC). In Fabric these views are removed and deleted by the framework when the ReactShadowNode is destroyed.

Reviewed By: shergin

Differential Revision: D10319737

fbshipit-source-id: 2e2d2599006cd8205e0153c18cd75383387ce1df

Author: mdvacca

ReactAndroid/src/main/java/com/facebook/react/ReactInstanceManager.java

@@ -1073,7 +1073,11 @@ private void tearDownReactContext(ReactContext reactContext) {
 
     synchronized (mAttachedRootViews) {
       for (ReactRootView rootView : mAttachedRootViews) {
-        rootView.removeAllViews();
+        if (rootView.getUIManagerType() != FABRIC) {
+          // All the views created in surfaces that are managed by Fabric, are removed and deleted
+          // by the Mounting Layer.
+          rootView.removeAllViews();
+        }
         rootView.setId(View.NO_ID);
       }
     }