TrafficCaptureHandler is at wrong place in KV pipeline

Suggested release note:

When KV traffic capture is enabled, each 
`ReadTrafficCapturedEvent` now contains a single protocol frame, and the human-readable frame description is more accurate.

TrafficCaptureHandler tries to dissect Couchbase Binary Protocol packets if it's capturing traffic on a KV connection. However, MemcacheProtocolDecodeHandler appears in the pipeline after TrafficCaptureHandler, so traffic capture is not happening along packet boundaries, so the packet dissection sometimes fails or is misleading.