This reverts commit 5184d02a7c.
The decision was made to go with fstrim because it is faster and more
universal that zerofree. The related-id has the patchset that implements
fstrim.
Related-Id: I269b4416be450369616f9b8e030f84c30e329804
Change-Id: If40cf2fc0ecd8686768cbfeac9ecee90907674e7