Start Vold on early-fs

We need vold on early-fs so we can handle userdata checkpointing.
Without this, devices will take an extra minute or two as checkpointing
related vdc calls attempt to reach vold before it is available.

Bug: 134114000
Test: Boot, see vold has started before vdc checkpointing tries to call
      out to vold.

Change-Id: Idfdb304503a163fbb91f9317949eb98c06fecce1