[devtools] properly close open access on tearDown
avoiding further warning about living sessions while the repo is turned off.
The doc string says:
The RepoAccess need to be closed to destroy the associated Session.
TestCase usually take care of this aspect for the user.
but that wasn't true until now.
usr/bin/cubicweb-ctl usr/bin/
usr/lib/PY_VERSION/*-packages/cubicweb/cwctl.py
../cubicweb-ctl.bash_completion etc/bash_completion.d/cubicweb-ctl