[autotest] Ensure sl4a.apk is installed when running android_ACTS

Updates the android_ACTS test to ensure that sl4a is installed,
and if it is not installed and the device is within the lab
infrastructure then install it.

BUG=chromium:588348
TEST=Ran ./test_droid.py ZX1G22LL54,ZX1G22HV3T android_ACTS.BluetoothTest \
--remote android1758-row1-rack7-blth-test-station-1.cros and ensured the
test did not error out.

Change-Id: I332e5f7939dc1b29ec3a38e40049e2c46ae7229f
Reviewed-on: https://chromium-review.googlesource.com/328782
Commit-Ready: Simran Basi <sbasi@chromium.org>
Tested-by: Simran Basi <sbasi@chromium.org>
Reviewed-by: Simran Basi <sbasi@chromium.org>
Reviewed-by: Dan Shi <dshi@google.com>
1 file changed