Revert "update_engine: Add XZ compression for CrOS"

This reverts commit 717c324c.

Reason for revert: <canaries failed>

Original change's description:
> update_engine: Add XZ compression for CrOS
>
> This patch implements XZ compression for Chrome OS. It is only activated
> for only delta payload at this point. The XZ compression is typically
> slower than Bzip2 to compress, but faster to decompress. However, it
> uses slightly higher memory in decompression. It compresses about 5%-10%
> better than the current Bzip2.
>
> BUG=chromium:758792
> TEST=unittests pass; brillo_update_paylod {generate|verify} passes;
>
> Change-Id: Icdaf1d37d344c30a796845eb64daa00120f3598a
> Reviewed-on: https://chromium-review.googlesource.com/811895


> Commit-Ready: Amin Hassani <ahassani@chromium.org>
> Tested-by: Amin Hassani <ahassani@chromium.org>
> Reviewed-by: Alex Deymo <deymo@chromium.org>
> Reviewed-by: Ben Chan <benchan@chromium.org>

TBR=benchan@chromium.org,deymo@chromium.org,deymo@google.com,senj@chromium.org,ahassani@chromium.org

Change-Id: I43e8c5ebec84d395b87aa782fb4d478a5fe99279
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromium:795313
Reviewed-on: https://chromium-review.googlesource.com/830053


Commit-Ready: Amin Hassani <ahassani@chromium.org>
Tested-by: Amin Hassani <ahassani@chromium.org>
Reviewed-by: Amin Hassani <ahassani@chromium.org>
Reviewed-by: Ben Chan <benchan@chromium.org>