Add unit tests for check_lab_status() internals

This refactors check_lab_status for testability, and adds unit tests
to cover all of the function's code paths.

BUG=None
TEST=run the unit tests

Change-Id: I7cbeb41314af541aea17405c0f50ea54ae2bbc50
Reviewed-on: https://chromium-review.googlesource.com/178307
Tested-by: Richard Barnette <jrbarnette@chromium.org>
Reviewed-by: Simran Basi <sbasi@chromium.org>
Commit-Queue: Richard Barnette <jrbarnette@chromium.org>
2 files changed