[notification] avoid using InternalManager when we've got a CWUser This will avoid potential information leak due to missed security restriction and is more compatible with legacy code (pb encountered in some client code). Closes #10294761

usr/bin/cubicweb-ctl usr/bin/
usr/lib/python2*/*-packages/cubicweb/cwctl.py
../cubicweb-ctl.bash_completion etc/bash_completion.d/cubicweb-ctl