* Change settings default
* Set `ENABLE_CREATOR_GROUP` to False for devstack
* Set `ENABLE_CREATOR_GROUP` to False for tests

In f095c5fe it was decided to enable
anyone to make courses in Studio by default in order to make things
easier in dev environments. This was before the code was open source.
This default is likely in effect for many Open edX instances, but almost
no one would want this setting outside of development.

Cherry picked from #15343 6b085281.