[repo] Don't crash on start when fs schema is missing some db schema entities This occurs usually while developping and we don't want systematically to rebuild the database to start the instance or run e.g. i18ninstance.

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