Respect android:allowBackup="false" during full backup & restore

Packages with this manifest attribute set 'false' will not be backed
up even through the "full device backup" infrastructure.  If someone
produces an apparent restore file with data for such an application,
it will not actually be restored onto the device.

When an apk is installed during the course of a restore operation,
it is validated against the manifest contents and deleted if there
is a mismatch.  Also, if the newly-installed app is found to
disallow backups, no file content will be processed for that app.

Bug 4532159

Change-Id: I59630054584b1394e567de939192e22e597044ee