Backup firmware in tests which will modify firmware

Use backup_firmware() (in faftsequence) before testing, and restore_firmware()
(in faftsequence) after testing.

BUG=chromium-os:33641
CQ-DEPEND=32504
TEST=run_remote_tests.sh --servo [test]

Change-Id: I5fd927f4855df9d5ddb5fc3e458f4c83be244b51
Reviewed-on: https://gerrit.chromium.org/gerrit/32528
Reviewed-by: Tom Wai-Hong Tam <waihong@chromium.org>
Commit-Ready: Tom Wai-Hong Tam <waihong@chromium.org>
Tested-by: Tom Wai-Hong Tam <waihong@chromium.org>
14 files changed