hv_netvsc: move VF to same namespace as netvsc device

When VF is added, the paravirtual device is already present
and may have been moved to another network namespace. For example,
sometimes the management interface is put in another net namespace
in some environments.

The VF should get moved to where the netvsc device is when the
VF is discovered. The user can move it later (if desired).

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