[devtools] Avoid db_cache collisions and mis-loading This is done by stopping to share the db_cache between TestDataBaseHandler instances It may seem overkill, but is the only way I could get it to work properly. I think the whole db caching code needs some rework to better work with different db handlers. Closes #4601328

if versions_map['cubicweb'][0] == (3, 7, 4):
    config['http-session-time'] *= 60
    config['cleanup-session-time'] *= 60
    config['cleanup-anonymous-session-time'] *= 60