xbuddy: Use the right location suffix for Project SDK artifacts.

Project SDK builds upload locations have a unique suffix that
distinguishes from ordinary Chrome OS builds. This lets us find them. We
do this by introducing a new config section LOCATION_SUFFIXES that
allows to associate a non-default suffix to path aliases, and adding an
entry for the 'project_sdk' alias.

BUG=brillo:586
TEST=Unit tests
TEST=cros flash --project-sdk finds the panther_embedded SDK image.

Change-Id: Ib0e926cd5f84fd084316222233acb2bf88349907
Reviewed-on: https://chromium-review.googlesource.com/260068
Tested-by: Gilad Arnold <garnold@chromium.org>
Reviewed-by: Don Garrett <dgarrett@chromium.org>
Commit-Queue: Gilad Arnold <garnold@chromium.org>
3 files changed