update tests for TaskPackageDropbox

[TaiSakuma]

• update tests for TaskPackageDropbox
  • the current tests only cover limited situations
  • what to vary
    • the number of tasks, e.g., 0, 1, or 5
    • the number of fails before success for each task, for example, [0, 0, 0, 0, 0], [0, 0, 2, 0, 0], [0, 1, 1, 0, 1] if the number of tasks is 5.
    • sequences of runs in poll
      • permutation
      • the number of runs in each pol