Flaky tests

[mthrok]

• tests/spdl_unittest/pipeline/pipeline_builder_test.py::test_periodic_dispatch_smoke_test
  https://github.com/facebookresearch/spdl/actions/runs/19344946897/job/55343248024?pr=1125
• tests/spdl_unittest/dataloader/dataloader_test.py::TestDataLoader::test_dataloader_aggregate
  https://github.com/facebookresearch/spdl/actions/runs/19416443156/job/55545894379?pr=1136
  https://github.com/facebookresearch/spdl/actions/runs/19894282258/job/57021080741#step:6:1
  https://github.com/facebookresearch/spdl/actions/runs/20476999634/job/58843577285?pr=1265#step:6:1322
• TestNvdecThreadLocalCaching.test_decoder_caching_different_threads
  https://github.com/facebookresearch/spdl/actions/runs/20183287615/job/57948484159?pr=1242#step:6:674