Shutdown process take very long time when using NetworkManager to connect to network (I use WIFI) and network filesystem is active. In shutdown process NetworkManager service stop first and wifi adapters disconfigured. Then netfs service try to umount active connections to network shares (CIFS for example) and can't do it very long time (CIFS response timeout), because network manager is already stopped and wi-fi network adapters disassociate. Workaround is that NetworkManager must start before netfs and stop after netfs.
F9 and later fix this; unfortunately it's not possible to redo all the init priorities on F8.