To return the regenerated CAS for SET_WITH_META / ADD_WITH_META

set/add with meta can update the CAS of a vbucket to any value - a faulty input can "poison" the max_cas of the vbucket - affecting the hybrid logical clock logic (and impacting LWW XDCR).
KV offers two modes of protection to prevent the above

1. Error - If the input CAS exceeds the current wall clock time by a configured threshold,KV rejects the operation and an error is returned.
2. Replace - In this mode KV accepts the operation but the CAS is regenerated.

Currently if the protection is set to replace mode, CAS in the response for Add/Set with meta is set to the input provided (poisoned CAS) instead of the newly generated CAS.