Make RescueParty call vold directly

This changes RescueParty to call vold over binder directly for
Checkpointing related calls. It turns out that if the system is in a bad
enough state, the other method would not work, as some of the services
required would not be running.

Bug: 135558798
Test: setprop persist.sys.enable_rescue 1
      setprop debug.crash_system 1 or setprop debug.crash_sysui 1
      vdc checkpoint startCheckpoint 3
      stop
      start
      Device should go through the rescueparty flow, and reboot.
      Repeat without checkpoint. Device should prompt reboot.

Change-Id: I8b11d68075cc291e9557d524bc87b54d17b370e4