build: get rid of the sparse expand stuff

* i don't see a reason why we are doing this because we never deal
with flashing system img rawly
* This will put useless write on ssd..
* we don't have space on ssd

Change-Id: Icd53d161b8515f5eca238b98ad68515d69caa34f

Conflicts:
	tools/releasetools/build_image.py