The Zeppelin charm deploys spark-client and zeppelin-server roles.
When zeppelin-server spark config is updated (e.g. we configure it in 'yarn' mode), the spark-client config is not updated. This is fine for jobs submitted through Zeppelin, but if a user attempted to spark-submit on the deployed machine, they may send their job to the wrong master.
Also, the zeppelin-spark test might stomp on top of a pre-deployed spark charm. Fix this by deploying a test-only copy of the spark charm, run the test, then remove the charm.