vm: use virtio-rng with host's /dev/urandom to fix boot delays with recent OS

slapos/recipe/vm.py

@@ -124,7 +124,10 @@ class BaseRecipe(EnvironMixin):
         raise
     return ['qemu-system-' + ARCH, '-enable-kvm', '-drive', drive,
             '-smp', self.options.get('smp', '1'), '-m', str(mem),
-            '-net', 'nic,model=virtio', '-net', net]
+            '-net', 'nic,model=virtio', '-net', net,
+            # https://daniel-lange.com/archives/152-hello-buster.html
+            '-object', 'rng-random,filename=/dev/urandom,id=rng0',
+            '-device', 'virtio-rng-pci,rng=rng0']
 
   @property
   def ssh_key(self):