GoXDCR Mutations Failed Resolution stat incorrect

This stat displayed in the UI from docs_failed_cr_source tracks the number of documents that were not replicated as they were not the winner of conflict resolution (e.g. they already exist on the destination cluster). It appears that this stat does not track accurately however:

• Spin up 2 clusters, A and B.
• Load beer-sample on A.
• Enable replication from A.beer-sample -> B.default
• Once all docs replicated, pause replication
• Restart replication
• On A, monitor Outgoing XDCR:
  When percentage complete reaches 100% (i.e. all docs have been checked), mutations failed resolution will sit at around 6400 (of 7303 total docs). This changes on subsequent runs with no obvious pattern.
• On B, monitor Incoming XDCR:
  No sets are seen, implying that (as expected) all docs on B are at their latest revision. Therefore all docs on A should have been listed as failed.