[CrOS Cellular] Fix two issues with FakeOtaActivator.

(1) Make the destructor virtual and override base class destructors.
(2) Remove extraneous #endif from the .cc file.

These issues were caught by vkuzkokov@ on
https://chromium-review.googlesource.com/c/chromium/src/+/1604213

Change-Id: I1f82c04139c57880a46acfe904a528853f589fe2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1628938
Auto-Submit: Kyle Horimoto <khorimoto@chromium.org>
Commit-Queue: Vladislav Kuzkokov <vkuzkokov@chromium.org>
Reviewed-by: Vladislav Kuzkokov <vkuzkokov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#663154}
2 files changed