[server] move connection pooler initialization logic to get_cnxset()
This avoid complex logic in Repository initialization.
Document: cubicweb-doc
Title: CubicWeb Documentation
Author: Logilab
Abstract: Some base documentation for CubicWeb users and developers
Section: Programming
Format: HTML
Index: /usr/share/doc/python3-cubicweb-documentation/html/index.html
Files: /usr/share/doc/python3-cubicweb-documentation/html/*