"force" activation on call retry only if object was activated during remote call

In JDK1.2beta2, an ActivatableRef will "force" activation (i.e., a call
to Activator.activate will visit the activation group for the object) on
almost every attempt at activation (unless the initial value of the remote
ref is null). Activation should only be forced, before a call is retried,
if the object was previously activated during the remote call. This will
allow the Activator's cached value of the ref to be used in many situations
rather than always visiting the remote object group on an activate request
(which is much more expensive since it requires an extra round-trip call
to the remote group).