Merge branch 'jk/lsan-race-ignore-false-positive'

The code to check LSan results has been simplified and made more
robust.

* jk/lsan-race-ignore-false-positive:
  test-lib: add a few comments to LSan log checking
  test-lib: simplify lsan results check
  test-lib: invert return value of check_test_results_san_file_empty