no network for genericcloud

[Thomas Koch <thomas@koch.ro>]

I'm learning qemu and cloud-init bottom up and am currently stuck getting the network / internet working.

~/testvirt/user-data.yml:

```
#cloud-config
users:
  - name: thk
    lock_passwd: False
    plain_text_passwd: pass
```

create.sh:

```
#!/bin/sh

WORKIMG=~/tmp/debian-11-genericcloud-amd64_work01.qcow2
CLOUDINITISO=~/tmp/cloud-init.iso

test -e $WORKIMG && rm $WORKIMG
qemu-img create -f qcow2 \
         -b ~/testvirt/debian-11-genericcloud-amd64-daily-*.qcow2 \
         $WORKIMG

test -e $CLOUDINITISO && rm $CLOUDINITISO
cloud-localds $CLOUDINITISO  ~/testvirt/user-data.yml

qemu-system-x86_64 \
    -smp cpus=3 \
    -nographic \
    -m 1G \
    -hda $WORKIMG \
    -hdb ~/tmp/cloud-init.iso \
    -net nic -net user
```

The VM has only a loopback device after running create.sh. What am I missing?

Thank you!