Stop using (and remove) deprecated SetSystemSaltPath API

There's a deprecated function in libchromeos to set the path of
the file in which the systemwide cryptographic salt value is
stored. Stop using it, and delete it.

BUG=chromium:378836
TEST=build platform2 and chromeos-login, run unit tests.
TEST=paladin trybot

Change-Id: I08ae6129c00921b57b8a5ffc7d59998b2c18f47c
Reviewed-on: https://chromium-review.googlesource.com/202508
Tested-by: Chris Masone <cmasone@chromium.org>
Reviewed-by: Darren Krahn <dkrahn@chromium.org>
Commit-Queue: Chris Masone <cmasone@chromium.org>
3 files changed