Reland qsr's "Use adb reverse instead of forwarder2"
Reland qsr's "Use adb reverse instead of forwarder2"

Original CL: https://codereview.chromium.org/868453006
That was reverted because the bots didn't support adb reverse(?).

The Android bots have been upgraded to Lollipop, afaik.
This CL continues using pylib's constants.GetAdbPath for now.

BUG=NONE
R=qsr@chromium.org, ppi@chromium.org
TEST=apptests pass on Android bots.

Review URL: https://codereview.chromium.org/912023005

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