Handle corrupt packages.xml

If the device hard reboots or is otherwise killed
between write and fsync of packages.xml, it can write all zeros. This is
not a problem in most cases as packages.xml is renamed to
packages-backup.xml before writing begins. In the case (boot after a
failed first boot) that a packages.xml does not exist, we may read that
all 0 packages.xml. In such a case we will encounter IOExceptions and
will not get the opportunity to build the VersionInfos that we require
later during boot.

This change adds a finally block for those exception cases to populate
the VersionInfos to adequately handle subsequent stages of boot.

Fixes: 178518634
Bug: 178518634
Test: manual; adb shell 'stop; rm /data/system/packages.xml; fallocate -l 1K /data/system/packages.xml; start'
Change-Id: I532b2bcd5b739345c8cd2e3f3a3d9a6393f68fba