merge with 3.21.3
The change in unittest_serverctl.py is needed because of daef7ce08fea
(from 3.20.11) and 3914388b2d0f (from the 3.22 branch). Due to both
changes, CubicWebTC.config.repository no longer creates a new repository
(and thus, a new connection). Since both DBDumpCommand and
CubicWebTC.tearDown try to shutdown the repo, tearDown breaks apart.
The solution is to temporarily disable ServerConfiguration's config
cache. By forcing DBDumpCommand to get a new configuration object, it
then gets its own Repo object, allowing tearDown and DBDumpCommand to
work independently.
rql('SET X name "BoundaryConstraint" '
'WHERE X is CWConstraintType, X name "BoundConstraint"')