Add operator user to created roles by default

[tstenner]

Creating a database fails unless the operator user is either SUPERUSER (not the case in some public clouds) or is in the new owner role.

The issue can be reproduced locally with a non-superuser role:

CREATE ROLE pgoperator WITH
	PASSWORD 'pgoperator'
	LOGIN
	CREATEDB
	CREATEROLE;

GRANTing the created role to the operator user is already done as a workaround for some clouds, but it should be done by default. It doesn't hurt when the user has SUPERUSER privileges and makes some already implemented and needed workarounds (e.g. for the IBM cloud) unnecessary.