Fix some failing/failing flaky tests

[wileyj]

There are a few tests that are either flaky or failing, likely they were missed in previous PR's since they only ever run when the a release workflow is called:

flaky: tests::epoch_21::test_v1_unlock_height_with_current_stackers - this passes usually on retry

failing:

tests::neon_integrations::atlas_integration_test
tests::epoch_21::test_sortition_divergence_pre_21
tests::epoch_21::test_pox_reorg_flap_reward_cycles

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