[fix] AsyncStorage.flushGetRequests

Add stub function for API compatibility.

Close #676

src/apis/AsyncStorage/index.js

@@ -61,6 +61,11 @@ export default class AsyncStorage {
     }, callback);
   }
 
+  /**
+   * (stub) Flushes any pending requests using a single batch call to get the data.
+   */
+  static flushGetRequests() {}
+
   /**
    * Gets *all* keys known to the app, for all callers, libraries, etc.
    */