servo: Make dut-power read SERVOD_PORT just like dut-control

BUG=none
TEST=dut-power --port 9002; SERVOD_PORT=9002 dut-power; dut-power
Made sure it connected correctly.

Change-Id: I5bc3d8cff3a3bfb10addf42174c40081fca26e85
Reviewed-on: https://chromium-review.googlesource.com/1258592
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Tested-by: Raul E Rangel <rrangel@chromium.org>
Reviewed-by: Ruben Rodriguez Buchillon <coconutruben@chromium.org>
2 files changed