Clean up properly if outcall for doRestoreFinished() fails

The target app crashed at an inopportune time but this shouldn't
invalidate the whole ongoing restore operation; it's a problem local to
the specific app undergoing restore.  Recognize this, clean up the app's
possibly-incomplete data, and continue running the restore queue as
planned.

Bug 23228982

Change-Id: If9a19d2fe6a0ce5339c893630d7a61a5a5ccd9b1