Add a tear-down script for devices used in ART target testing.

This script is meant to undo (most of) the set-up work done by
tools/setup-buildbot-device.sh.

Test: art/tools/setup-buildbot-device.sh && art/tools/teardown-buildbot-device.sh
Bug: 34729697
Change-Id: I4a16d8451f5be461121ca9492dd5e732177bd719
3 files changed