[devtools] Fix database creation issues for CubicWebTestTC tests
To reproduce (with a purged repo):
* python web/test/test_jscript.py
* python web/test/unittest_views_xmlrss.py
The '__default_empty_db__' will contain the wrong 'base_url'
configuration, thus breaking URLs in the xmlrss tests.
Closes #9297611.
addressbook
basket
blog
book
calendar
comment
company
email
file
folder
i18ncontent
keyword
link
mailinglist
person
tag
timeseries
vcsfile