qemu: fix regression in update-device for interfaces

qemu: fix regression in update-device for interfaces

Commit a37bd2a15b8f2e7aa09519c86fe1ba1e59ce113f eliminated a failure
to update *any* change in an interface that was connected via a
network that consisted of a pool of VFs using macvtap passthrough
mode. Unfortunately it caused a regression that results in failure to
update changes to bandwidth/vlan/trustGuestRxFilters in any interface
connected via a network that uses a bridge to connect tap devices.

This fixes that problem by narrowing the usage of the fix in the
earlier patch to only be done in the case that the the interface is
connected via a macvtap+passthrough network.

Signed-off-by: Laine Stump <laine@redhat.com>
Fixes: a37bd2a15b8f2e7aa09519c86fe1ba1e59ce113f
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>