[cassandra2] Update to use the new driver version
[cassandra2] Update to use the new driver version

Fixes #612.

madhurihn/YCSB_ToyDB,ChristianNavolskyi/YCSB,brianfrankcooper/YCSB,jaemyoun/YCSB,leschekhomann/YCSB,leschekhomann/YCSB,brianfrankcooper/YCSB,brianfrankcooper/YCSB,zyguan/ycsb,madhurihn/YCSB_ToyDB,ChristianNavolskyi/YCSB,cricket007/YCSB,ChristianNavolskyi/YCSB,manolama/YCSB,leschekhomann/YCSB,madhurihn/YCSB_ToyDB,zyguan/ycsb,ChristianNavolskyi/YCSB,cricket007/YCSB,zyguan/ycsb,manolama/YCSB,manolama/YCSB,cricket007/YCSB,manolama/YCSB,madhurihn/YCSB_ToyDB,jaemyoun/YCSB,jaemyoun/YCSB,jaemyoun/YCSB,leschekhomann/YCSB,cricket007/YCSB,zyguan/ycsb,brianfrankcooper/YCSB