bus/vmbus: skip non-network devices

bus/vmbus: skip non-network devices

The vmbus scan code can just skip non-network devices.
More importantly, this fixes the bug where some vmbus devices
don't have all the attributes (like monitor_id) and a single
failure would cause the scan to break the loop.

Fixes: 831dba47bd36 ("bus/vmbus: add Hyper-V virtual bus support")
Cc: stable@dpdk.org
Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>