Update accessories test keys location

Move around the test keys used for standalone accessories signing
unittesting, so they are easier to use.

BRANCH=smaug, samus
BUG=chrome-os-partner:46635
TEST=run cros-signing unittests (./signing_unittests.py)

Change-Id: I02fcf444ec76bf6ebf6eb477e1236869aa877210
Reviewed-on: https://chromium-review.googlesource.com/309967
Commit-Ready: Vincent Palatin <vpalatin@chromium.org>
Tested-by: Vincent Palatin <vpalatin@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
4 files changed