End the deflater when closing a ZipOutputStream.

I'm not particularly happy with ZipOutputStream.close() because it
doesn't call super.close(). Fixing it to call super.close() has two
problems: finish() will be called conditionally (we want it always)
and it won't null out 'out', which is observable to subclasses.

git cherry-pick -e 1d5c4e84a256e76de529b27e7e28ed48f126fe7b
http://b/3187485

Bug: 3223687