[devtools] Set dumb value for postgres's db-host to avoid unexpected connection to a local server Currently, if something goes wrong (eg config built before call to startpgcluster) while a pg server is running on localhost, it may connect to this server and run the test in there unexepectedly.

../../doc/book usr/share/doc/cubicweb-documentation
../../doc/_build/html usr/share/doc/cubicweb-documentation