Fix file descriptor leak when opening invalid archives.

I've inspected all other callers of OpenArchive and this seems
to be the only broken one. The easiest way to reproduce this is
by using getPackageArchiveInfo or by adding an asset path that
isn't a valid APK.

bug: https://code.google.com/p/android/issues/detail?id=171099
Change-Id: I41cd85d20f26ad47968e2a6f1384cc03330b558b