[server/session] make commit/rollback obey ensure_cnx_set
Inside the ensure_cnx_set context manager, commit and rollback aren't
allowed to dispose of the cnxset.
Document: cubicweb-doc
Title: CubicWeb documentation
Author: Logilab
Abstract: Some base documentation for CubicWeb users and developpers
Section: Apps/Programming
Format: HTML
Index: /usr/share/doc/cubicweb-documentation/index.html
Files: /usr/share/doc/cubicweb-documentation/*.html