vmm: api: Match VhostUserNetConfig defaults between CLI and HTTP API

In order to let the CLI and the HTTP API behave the same regarding the
VhostUserNetConfig structure, this patch defines some default values
for num_queues, queue_size and mac.

num_queues is 2 since that's a pair of TX/RX queues, queue_size is 256
and mac is a randomly generated value.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

vmm/src/api/openapi/cloud-hypervisor.yaml

@@ -375,17 +375,16 @@ components:
     VhostUserNetConfig:
       required:
       - sock
-      - num_queues
-      - queue_size
-      - mac
       type: object
       properties:
         sock:
           type: string
         num_queues:
           type: integer
+          default: 2
         queue_size:
           type: integer
+          default: 256
         mac:
           type: string