Adds temporary chown to sparse_copy.
Adds temporary chown to sparse_copy.

`sparse_copy` needs read and write access to the devices. Since we
cannot shell out to a run-as-root command here, we temporarily take
ownership of the device.

Change-Id: I891c38dbcba7177286dca729684c88ac065bd085

n0ano/gantt,n0ano/gantt