autotest: network_ui: Added test_utils.py

Added common code to test_utils.py

BUG=chromium:264107
TEST=network_ChromeCellularSmokeTest

Change-Id: Ifdda4f59c472d6589d36a9100669c8451a6f953a
Reviewed-on: https://gerrit.chromium.org/gerrit/65274
Commit-Queue: Arman Uguray <armansito@chromium.org>
Reviewed-by: Arman Uguray <armansito@chromium.org>
Tested-by: Arman Uguray <armansito@chromium.org>
2 files changed