ThresholdLogTracing output missing fields in first operation

When using the threshold logging tracer the first operation seems to be missing last_operation_id and last_local_id (based off of http://review.couchbase.org/c/94976/4/tracing.go, otherwise missing operation_id).

example output, the erroneous operation is opaque 0x5 and occurs before the Replace.:

{ "service": "kv", "count": 6, "top": [ { "operation_name": "Get", "total_us": 31903, "server_us": 22, "decode_us": 91 }, { "operation_name": "Get", "total_us": 1204, "server_us": 8, "last_operation_id": "0x7", "last_local_id": "2f87cf1799fe15fd\/cda32b624efa3e53" }, { "operation_name": "Get", "total_us": 1166, "server_us": 14, "last_operation_id": "0xa", "last_local_id": "2f87cf1799fe15fd\/cda32b624efa3e53" }, { "operation_name": "Replace", "total_us": 422, "encode_us": 15, "server_us": 49, "last_operation_id": "0x6", "last_local_id": "2f87cf1799fe15fd\/cda32b624efa3e53" }, { "operation_name": "Get", "total_us": 407, "server_us": 8, "last_operation_id": "0x9", "last_local_id": "2f87cf1799fe15fd\/cda32b624efa3e53" }, { "operation_name": "Get", "total_us": 385, "server_us": 8, "last_operation_id": "0x8", "last_local_id": "2f87cf1799fe15fd\/cda32b624efa3e53" } ] }