Gateway must handle 5-10 config updates per second

[sdpeters]

This is one of the initial gateway project requirements

The requirement says "Handle configuration updates (creates, deletes, etc.) in the order of around 5 updates/sec on average at the Ceph cluster level, expecting burstiness of 10 updates/sec or more."

We might need to clarify the difference between a config update being handled, and being complete. For example, the removal of a namespace may require one or more gateway nodes to wait for in-flight IO to complete, or at least to ensure that no more IO will be submitted to RBD for that namespace. It might require those gateways to wait for confirmation from all affected hosts that they've acted on the namespace removal (I don't think the exact behavior has been defined).