Matching engine latencies keep going up with sync match disabled

[tamer-eldeeb]

[tamer-eldeeb]

We observed that when executing CAS queries on static fields, the coordinator issues a range query during the read phase of paxos with LIMIT 1.
This is problematic, as it causes table scans when only a point query is needed.
(cf. http://thelastpickle.com/blog/2017/03/07/The-limit-clause-in-cassandra-might-not-work-as-you-think.html)