[devtools] even better: use a plain Connection (server-side) object for pre_setup
The previous commit switched from passing a Session to a
ClientConnection.
This fixes unittest_ldapsource's pre_setup_database, which relied on a
server-side object to get at the repo.
usr/lib/PY_VERSION/*-packages/cubicweb/server/
usr/lib/PY_VERSION/*-packages/cubicweb/hooks/
usr/lib/PY_VERSION/*-packages/cubicweb/sobjects/
usr/lib/PY_VERSION/*-packages/cubicweb/schemas/
usr/share/cubicweb/migration/