[NetKVM] Proper device features acknowledgement
[vioserial] Moved to the new feature management API
[balloon] Moved to the new feature management API
[viostor] Moved to the new feature management API
[virtiolib] Old feature management API dropped
[NetKVM] Control queue initialization fixed
[virtio-serial] bz#823818: rewrote the driver's write function.

The previous write function didn't handle well the case when the
virtqueue was full and caused the guest to stop responding. New
implementation fixed that and add a support for a non-blocking
write (returns immediately if write will block).
[viortio-serial] bz#902150: driver was unusable after sleep/suspend.

The serial ports was flagged as "removed" after sleep/suspend. This
caused an error then trying to access the driver.