recover_duts: Reimplement as shell script

In certain autotest failure cases /var gets wiped and with it the
Python interpreter, in such a situation recover_duts.py can't be
executed. The script is fairly simple and doesn't really benefit
from being implemented in Python, reimplement it as shell script.

BUG=chromium:882015
TEST=touch /mnt/stateful_partition/.labmachine
  rmmod r8152 # or applicable ethernet driver
  # wait up to 90s
    => eth0 is brought up again
CQ-DEPEND=CL:1217082

Change-Id: I07a4610056c83e88f1b19e7e2f8b7767f81254e2
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1213409
Reviewed-by: Douglas Anderson <dianders@chromium.org>
3 files changed