Don't install ssh keys via mod_for_test_scripts.

The test image ssh keys are now delivered as a separate package,
so mod_for_test_scripts/350addTestAuthKeys no longer needs to
add the keys to test images.  Additionally, this deletes support
for `build_image --nostandard_backdoor`, since that feature
depended on the 350addTestAuthKeys script.

The 350addTestAuthKeys is replaced with 350addEnvironment, in order
to preserve additional settings needed for the 'su' command to
function properly.

BUG=chromium:322748
TEST=test ssh to a test image, test 'su' on a test image

Change-Id: Ifc4877f2b7f55ca52e657fe1714751227d71e27e
Reviewed-on: https://chromium-review.googlesource.com/217771
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Tested-by: Richard Barnette <jrbarnette@chromium.org>
Commit-Queue: Richard Barnette <jrbarnette@chromium.org>
4 files changed