Add IT that runs concurrent Fluo instances using same zookeepers

Thought of this while reviewing #299. It would be nice to have an IT that test running two concurrent Fluo instances (w/ different zk chroots) that use the same zookeepers. The purpose of the test would be to ensure the two instances do not interfere w/ each other.

Review issue #299 and the repository's existing integration-test setup first; no specific file or test entry point is named here. Add an integration test that runs two Fluo instances concurrently against the same ZooKeeper service with different chroots, and verify that their operations do not interfere with each other.

Written by the indexing model from the issue text.