[batch] fix flaky batch invariants test (#9509)
[batch] fix flaky batch invariants test (#9509)

I have added an item to services design meeting to further discuss the meaning of
`start_time` and `end_time` of an attempt. For the time being, this eliminates the
flakiness that is preventing PRs from merging.
hail-is/hail,cseed/hail,cseed/hail,hail-is/hail,cseed/hail,cseed/hail,cseed/hail,danking/hail,danking/hail,hail-is/hail,danking/hail,danking/hail,cseed/hail,cseed/hail,hail-is/hail,danking/hail,danking/hail,hail-is/hail,hail-is/hail,hail-is/hail,cseed/hail,danking/hail,hail-is/hail,danking/hail