Re-enable caching step in RS filters

Bug: 8478659
Bug: 8459181
Bug: 8450339
Bug: 8457323

With the compatibility library, different Scripts instances
actually points to the same thing. We thus need to explicitely
rebind all the variables to the correct script instance before
running RS filters...

Change-Id: Id6cd4e44b5a67a3d2588e158c616b2b44e214a5b