Fix race in DefaultConfigProvider.checkAndApplyConfig

Suggested release note:

When the SDK receives multiple cluster map versions at the same time, it is now more careful about applying only the most recent version. Before this change, there was a brief window where the SDK could apply an obsolete cluster map. If this happened, the SDK would temporarily dispatch requests to incorrect or non-existent nodes. This condition was typically short-lived, and healed the next time the SDK polled for an updated cluster map, or dispatched a KV request to the wrong node.