Use correct call in PDO_CASSANDRA_ATTR_RANDOMIZE

Use setRandomize() call instead of setMaxConsecutiveFailures() in
PDO_CASSANDRA_ATTR_RANDOMIZE case.


PDO_CASSANDRA_ATTR_RANDOMIZE doesn't works because it call the wrong thrift function.

Furthermore, I have a problem when I initialize a pdo connection with several servers, the driver always connect to the same "random" host. Randomize might be broken on thrift cpp side (lib/cpp/src/thrift/transport/TSocketPool.cpp, no salt initialisation ?), so random_shuffle always return the same result. Need to dig deeper though.