[BZ 1075575] Update Cassandra to a version specially crafted to not print the superfluous warning about OpenJDK.
BZ 823965 Maintain existing agent-configuration.xml and log4j.xml files after agent auto-update.
The new configuration will be kept in agent-configuration.xml.new and log4j.xml.new
so that we at least provide the user with the updated defaults in case they want to manually merge them.