[server/test] use server config in migration This allows a lighter initialisation (no rtag needed). Execution of those test move from 300 secondes to 220 seconds here. A 25% speedup

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