Tests - check clean WFQ; wave spacing (#124)

Check queue is clean after the one-at-a-time rate limited test.

test_one_at_a_time_with_limiter did not check
`queue_entries_are_cleaned_up`, but the test it copied from
(test_one_at_a_time) did.

Also, the wave spacing calc looked sus to me.

Give a little more tolerance on the calculations. GH runner is failing
them occasionally - for example off by .14s where the tolerance was
.1...

Author: chuck-dbos

tests/test_queue.py

@@ -121,6 +121,7 @@ def workflow_two() -> None:
     assert handle2.get_result() == None
     assert flag
     assert wf_counter == 1
+    assert queue_entries_are_cleaned_up(dbos)
 
 
 def test_queue_childwf(dbos: DBOS) -> None:
@@ -226,11 +227,12 @@ def test_workflow(var1: str, var2: str) -> float:
     # Verify that each "wave" of tasks started at the ~same time.
     for wave in range(num_waves):
         for i in range(wave * limit, (wave + 1) * limit - 1):
-            assert times[i + 1] - times[i] < 0.1
+            assert times[i + 1] - times[i] < 0.2
 
     # Verify that the gap between "waves" is ~equal to the period
     for wave in range(num_waves - 1):
-        assert times[limit * wave] - times[limit * wave - 1] < period + 0.1
+        assert times[limit * (wave + 1)] - times[limit * wave] > period - 0.2
+        assert times[limit * (wave + 1)] - times[limit * wave] < period + 0.2
 
     # Verify all workflows get the SUCCESS status eventually
     dbos._sys_db.wait_for_buffer_flush()