Make RescueParty not wipe if checkpointing

If we're checkpointing, we can roll back instead of wiping. If the
update was the problem, we will succeed. Otherwise, RescueParty will
catch the issue again and prompt the wipe later

Test: setprop persist.sys.enable_rescue 1
      Set device to not commit checkpoints
      vdc checkpoint StartCheckpoint 3
      reboot
      adb shell setprop debug.crash_system 1
      adb shell stop
      adb shell start
      Rescue Party causes reboot instead of wipe
      repeat without checkpointing to get wipe
Change-Id: Iba0263214baa7a0c3d5565b4393d03f975d8000a