Add configurable timeout options for Cassandra 1.2

The [Thrift timeouts can be configured][1] but we hadn't added the options to
the cassandra.yaml. This just adds the attributes with the same default
as the file already had.

[1]: http://www.datastax.com/documentation/cassandra/1.2/webhelp/index.html?pagename=docs&version=1.2&file=index#cassandra/configuration/configCassandra_yaml_r.html