- Don't connect right away in ha_cassandra::open. If we do this, it becomes 
  impossible to do SHOW CREATE TABLE when the server is not present. 
- Note: CREATE TABLE still requires that connection is present, as it needs 
  to check whether the specified DDL can be used with Cassandra.  We could
  delay that check also, but then one would not be able to find out about 
  errors in table DDL until they do a SELECT.