Configuration example for jwt multi tenancy

@sscarduzio
When a user logs in I see the following line in the logs.

 [16:39:07.618] [warning][readonlyrest_kbn:ensureIndexExists] error writing default space to .kibana {}

I made a post about this as well: Error writing to defaul space .kibana {} - #3 by sscarduzio
Might be related?