TIMOB-16889: fix Android activity lifecycle events

See explanation and test app in JIRA issue:
https://jira.appcelerator.org/browse/TIMOB-16889
It does not always cause a leak. But I think it's always safe to avoid circular references.
You used KrollFunction.call() which executes a function synchronously, so I supposed you wanted a synchronous function call. Do you really mean to use that? If you want an async call, you should use KrollFunction.callAsync() or callPropertyAsync().