[server] use sqls_create_multicol_unique_index to index entities.extid
SQL Server's UNIQUE is not standards compliant, it doesn't accept two
NULL values. Related to #7173702.
if versions_map['cubicweb'][0] == (3, 7, 4):
config['http-session-time'] *= 60
config['cleanup-session-time'] *= 60
config['cleanup-anonymous-session-time'] *= 60