netvsc: change logic for change mtu and set_queues

Use device detach/attach to ensure that no packets are handed
to device during state changes. Call rndis_filter_open/close
directly as part of later VF related changes.

Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>