Not ignoring authorization in data sources controller spec.
Use data source owner as logged in user.
[Finishes #59373328] Enable demo mode

 - Adds a demo_mode.enabled flag to chorus.properties
 - This mode disables some actions by non-admin users. The following actions are disabled:
  * db data source create, update, destroy
  * hdfs data source create, update, destroy
  * workspace/schema/csv import create
  * job create, update, destroy
  * workspace create, destroy