Fix stress for 2.1 in sstablesplit
Use 8 threads on write, otherwise default is 50
Write 1.5m iterations, grab/pass version to sstablesplit

- Succeeds on first pass, but ends with 9 split sstables second pass :(
Rename class to TestSSTableSplit
Write 1.1m rows to get 6 split tables both runs
More CQL tests
Merge branch 'master' of github.com:riptano/cassandra-dtest