[entity/url publishing] fetch_rqlst should use 'is_instance_of' instead of 'is' We usually want to get any subclasses as well (think Training subclass of Workcase). Closes #3210365.

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