Fix runtime restart: at com.android.server.backup.restore.FullRestoreEngine

When a full backup operation times out, resources are cleaned up
including closing and nullifying pipes. However FullRestoreEngine.restoreOneFile()
doesn't stop execution and can access the pipes causing RuntimeException.

This CL adds a flag to show whether the operation has timed out and
checks it before accessing the pipes.

Bug: 126244736
Test: 1) atest RunBackupFrameworksServicesRoboTests
      2) atest CtsBackupTestCases
      3) atest CtsBackupHostTestCases
      4) atest GtsBackupTestCases
      5) atest GtsBackupHostTestCases
      6) Manual: Test full backup/restore flow using Flipboard app

Change-Id: If400142a6fceaa4065409774bbff1cad8b4c6163