autotest (WiFi): refactor lucid sleep test init and cleanup

Refactor shared initialization and cleanup routines in
lucid sleep autotests into lucid_sleep_test_base, which
extends wifi_cell_test_base with wake-on-WiFi-related
actions.

BUG=None
TEST=Ran wifi_lucidsleep suite on samus and stumpy wificell servo DUTs. All
     tests ran successfully in both cases.
Change-Id: I6ce16887c5a158c362a34e3475680c93e18e98f6
Reviewed-on: https://chromium-review.googlesource.com/295315
Tested-by: Samuel Tan <samueltan@chromium.org>
Reviewed-by: Eric Caruso <ejcaruso@chromium.org>
Commit-Queue: Samuel Tan <samueltan@chromium.org>
8 files changed