Consistent clean up of failed installs.

Instead of remembering to add clean-up logic to every install scan
failure case, rely on the fact that we're now throwing for all errors
and use a finally clause to delete data directory when requested.

When clearing data for a package, always try deleting the app data
directories, even if no record of the package exists.  This helps
users recover from UID mismatches without resorting to a full data
wipe.

Bug: 17005516
Change-Id: I352863ef4e468c576ecf136549e21cceae2650d5