Randomly getting Error: Failed to decrypt report job data. with Kibana

@joelgriffith Hi, basically I run Kibana in DC/OS and all I do is scale up or down. So in essence each instance is running the exact same Docker/Marathon/config, I do not inject any special kibana.yaml in the docker container and use mostly default values except for the above mentioned config.

And then access Kibana through Haproxy.

The only thing I'm not sure is that "xpack.reporting.encryptionKey": "xxxxxx" if it's configurable by environment variable and if it should be XPACK_REPORTING_ENCRYPTION_KEY instead?