[migration] Improve update of in-memory schema during 3.18 CWAttribute.defaultval change
We weren't updating the schema properly so a bunch of structures still
had the old rdef with 'String' as object. That caused failures to add
new attributes later in the migration as their default value would be a
Binary object but the schema would expect a String.
Closes #3683640
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