XDCR - P2P - Merging peer node can introduce empty checkpoint

http://src.couchbase.org/source/xref/neo/goproj/src/github.com/couchbase/goxdcr/pipeline_svc/checkpoint_manager.go#2775
This function takes care of merging peer checkpoints with the local checkpoints.
There is a situation where if the current node has no checkpoint, and if a peer node returns an empty checkpoint (0 value for seqno, snapStart, etc), then this node’s checkpoint will be “polluted” and an empty checkpoint will be populated into the current node

Theoretically, it shouldn’t be a blocking issue, but this pollution should be fixed.