Add an autotest to simulate disconnects during channel switch

The test simulates both router initiated and client initiated disconnects
during channel switch. It is use to reproduce crbug/408370, and verify the
fix as well.

BUG=chromium:408378
TEST=Run this test on a peppy device

Change-Id: I4d4d387f9b88e33656da647dd8aedcadadfa9508
Reviewed-on: https://chromium-review.googlesource.com/217485
Reviewed-by: Peter Qiu <zqiu@chromium.org>
Tested-by: Peter Qiu <zqiu@chromium.org>
Commit-Queue: Peter Qiu <zqiu@chromium.org>
2 files changed