Description of problem:
When execute the refresh for the first time all Network Devices and Ports are saved successfully, but, from the second time onwards, some Network Devices are deleted and sometimes the ports are duplicated.

How reproducible:
Managing a physical server that has more than one Network Device

Steps to Reproduce:
1. Manage some LXCA with a physical server with more than one Network device
2. Perform the first refresh cycle
3. Inspect the guest_devices table in database and see that all data is saved successfully
4. Perform the refresh cycle again
5. Inspect the guest_devices table and see that only one Network Device (device_type = "ethernet") is associated to the physical server and probably the ports are now with the same name (it doesn't occur all the times)