CASSANDRA-20712 - disabling of constraints in CQLSSTableWriter

[smiklosovic]

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The Cassandra Jira

[bbotella]

If we are going to disable constraints, should we add the if check to this line? https://github.com/apache/cassandra/blob/trunk/src/java/org/apache/cassandra/cql3/statements/ModificationStatement.java#L1009

Validation.checkConstraints(metadata(), key);

And this? https://github.com/apache/cassandra/blob/trunk/src/java/org/apache/cassandra/cql3/statements/ModificationStatement.java#L1024

checkClusteringConstraints(clustering);