The problem is that the config.local.php is never being updated by the upgrade process, since it contains data that never should be changed automatically, like database settings, etc.
So please add these lines of the code in that file after these ones:
// Storage backend for sessions. Available backends: database, redis
$config['session_backend'] = 'database';
$config['session_redis_server'] = 'localhost';
$config['cache_apc_global_ttl'] = 0;
$config['cache_xcache_global_ttl'] = 0;