Race condition on topics creation.

[big-andy-coates]

Consider two calls to provision running in parallel. Both detect a topic doesn't yet exist in the cluster. Both try to create it. The first to try succeeds, the second will fail with a 'topic already exists' error.

Currently, this error is propagated to the caller. A better solution would be to gracefully handling this issue and just checking the topic has been created with the right config.