Add HELLO flag called DedupeNotMyVbucketClustermap

The KV engine introduces a new HELLO flag called DedupeNotMyVbucketClustermap with a value of 0x1e. Once this flag is negotiated, the node might send an empty body with NotMyVbucket (0x07) status codes. The KV engine tracks the revision that has been sent to the SDK over the socket connection, so a response with a NotMyVbucket status will only have a body if the pushed version is older than the active configuration.