Don't drop works under load w/StreamWorkManager/Kafka/storestate.enabled

With StreamWorkManager, Kafka, and nuxeo.stream.work.storestate.enabled=true, the server logs intermittently include the following WorkComputation WARN message indicating that the StreamWorkManager consumer is dropping a Work:

https://github.com/nuxeo/nuxeo/blob/5d81a4f7a93adedbd134e052e5f1c9039933c6fb/nuxeo-core/nuxeo-core-event/src/main/java/org/nuxeo/ecm/core/work/WorkComputation.java#L96

This typically occurs when lots of Works are being scheduled concurrently. In this case, it appears a state synchronization issue exists between the MongoDB KeyValueStore and the Kafka StreamWorkManager. See:

https://github.com/nuxeo/nuxeo/blob/5d81a4f7a93adedbd134e052e5f1c9039933c6fb/nuxeo-core/nuxeo-core-event/src/main/java/org/nuxeo/ecm/core/work/StreamWorkManager.java#L155

https://github.com/nuxeo/nuxeo/blob/5d81a4f7a93adedbd134e052e5f1c9039933c6fb/nuxeo-core/nuxeo-core-event/src/main/java/org/nuxeo/ecm/core/work/StreamWorkManager.java#L160

and

https://github.com/nuxeo/nuxeo/blob/5d81a4f7a93adedbd134e052e5f1c9039933c6fb/nuxeo-core/nuxeo-core-event/src/main/java/org/nuxeo/ecm/core/work/WorkComputation.java#L96

Specifically, our suspicion is that WorkComputation line 96 is being invoked from one thread in between the time lines 155 and 160 are invoked in another thread thus causing the dropped Work.