This patch fixes the following go vet warnings:
```
libcontainer/network_linux.go:96: github.com/vishvananda/netlink.Device
composite literal uses unkeyed fields
libcontainer/network_linux.go:114: github.com/vishvananda/netlink.Device
composite literal uses unkeyed fields
```
Signed-off-by: Antonio Murdaca <runcom@redhat.com>