Fix HMR after adding RA-Bundle groups

Summary:
The introduction of groups for random access bundles broke hot module reloading, because HMR uses a different Bundle class. And that didn’t have the `setRamGroups()` method.

This just adds an empty method on the base class.

**Test plan (required)**

I ran `node scripts/run-ci-e2e-tests.js --android`
Closes https://github.com/facebook/react-native/pull/9982

Differential Revision: D3886096

Pulled By: bestander

fbshipit-source-id: 46e6183607b0275d3cfe0d892360248b7b2154e9

react-packager/src/Bundler/BundleBase.js

@@ -88,6 +88,8 @@ class BundleBase {
     }
   }
 
+  setRamGroups() {}
+
   toJSON() {
     return {
       modules: this._modules,