Concurrent jobs are overlapping even with `maxConcurrency = 1`

[amitaibu]

I was trying this Seat reservation demo app, with latest master

In the past, when running multiple concurrent requests, it would get the seat reservations right. Currently, with latest master we get the following (notice the order and duplicate seat numbers):

We have set maxConcurrency = 1, so the Job should be processed one after the other

Steps to reproduce

1. Install repo
2. Goto http://localhost:8000/ShowEvent?eventId=7a7e856f-8475-48f5-977b-21bb85133a88
3. Copy the code and execute it on the command line - the code runs requets with parallel