Keep pgAdmin configuration writable

[cbandy]

The init container should have permission to write and replace these files. Kubernetes ensures the application container cannot write to them.

Checklist:

• Have you added an explanation of what your changes do and why you'd like them to be included?
• Have you updated or added documentation for the change, as applicable?
• Have you tested your changes on all related environments with successful results, as applicable?
  • Have you added automated tests?

Type of Changes:

• Bug fix

What is the current behavior (link to any open issues here)?

In some environments, the init container will fail with line 1: /etc/pgadmin/config_system.py: Permission denied.

Other Information:

Issue: PGO-1280