chroot version hooks: Add another binhost cleanup hook

The PARALLEL_POSTSUBMIT binhosts are being deleted. Add this
hook to cleanup sysroots after those land.

BUG=chromium:965244
TEST=None

Cq-Depend: chromium:1871742, chrome-internal:2015602
Change-Id: I35996c2ab1eb6645c2840c4c3404ebc1cbfa6b62
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosutils/+/1872377
Tested-by: Alex Klein <saklein@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
1 file changed