faft: restore kernel attributes if they are changed during tests

For tests that change kernel attributes such as priority and tries
flags, we should ensure the attributes get restored when the tests end.

BUG=chromium:215787
TEST=Pass all changed tests
TEST=Prioritize kernel B and run a test. Check the active kernel is
still B after the test ends.

Change-Id: I3212f1396f1abc7473b42308145d04e051b27422
Signed-off-by: Vic (Chun-Ju) Yang <victoryang@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/185325
Reviewed-by: Yusuf Mohsinally <mohsinally@chromium.org>
6 files changed