Flux end to end test aggregate_group_by_time_test is failing

This test passes in the `flux` repo, but is failing for some reason in `influxdb`.
```
--- FAIL: TestFluxEndToEnd (13.77s)
--- FAIL: TestFluxEndToEnd/testing/influxql (0.95s)
--- FAIL: TestFluxEndToEnd/testing/influxql/aggregate_group_by_time (0.18s)
end_to_end_test.go:199: found 1 tables that were not empty
```
It's unclear to my why the non-empty table is not shown in the test output.

Start with end_to_end_test.go around line 199 and run TestFluxEndToEnd/testing/influxql/aggregate_group_by_time. Trace how the failing table is checked and inspect the test output path; done means identifying why the table is non-empty and making the aggregate_group_by_time test pass with useful failure output.

Written by the indexing model from the issue text.