couchbase cli dcp consumer incorrect buffer acknowledgment

At the moment the dcp source pump sends buffer aknowledgment messages with the incorrect aknowledge size and opaque.

From the dcp documetation we see that the opaque value should be 0 and that "Only Mutation, Deletion, Expiration, Snapshot Markers, Set VBucket State, and Stream End messages should be buffered."

This is currently not the case and it is causing issue MB-32279