Enforce entity by connection limit more strictly

[acogoluegnes]

When creating producers/consumers at the same time in different threads, the coordinators may not be able to enforce the limit per connection. We then end up with 1 producer/consumer per connection.

One way to mitigate the issue is to create the entities synchronously or to sleep a few milliseconds between multi-threaded creations.

Way to reproduce: set 3 for the limit per connection, loop up to 9, create a consumer with an Executor. There should be 9 connections for the consumers (tested only with consumers).

Note adding too much synchronization can lead to deadlocks on recovery.