[autotest] test_droid V1.

This CL introduces test_droid, a script to launch autotest
tests against local Android DUTs connected to the host
computer via USB.

Much of the logic is similar to test_that, so this has all
been pulled into a new script test_utils.py

Pending work:

* Moving of generate_test_report to somewhere it is accesible
  outside of the chroot.
* Add in support for remote adb hosts (i.e. the DUT is
  connected to a remote computer).
* Sequences support.

BUG=b:25748759
TEST=./test_droid.py 7d52318 brillo_WhitelistedGtests
CQ-DEPEND=CL:315230

Change-Id: Idab3805f7921173fbc706354b322f37244240fa2
Reviewed-on: https://chromium-review.googlesource.com/314870
Commit-Ready: Simran Basi <sbasi@chromium.org>
Tested-by: Simran Basi <sbasi@chromium.org>
Reviewed-by: Aviv Keshet <akeshet@chromium.org>
9 files changed