When working locally it is nice to be able to run unstack.sh and not have too much extra stuff to clean up by hand before running stack.sh again. So clean up CEPH_DATA_DIR, contenta and mounts. Also fix a spot where '/var/lib/ceph' (the default value for CEPH_DATA_DIR) was hard-coded. Change-Id: I43ff06ca38f42ea4305b2c862902bf6f612e32f0