net: fix OptsVisitor memory leak

Fixes 96a1616c("qapi-dealloc: Reduce use outside of generated code")
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NJason Wang <jasowang@redhat.com>

net/net.c

@@ -1077,6 +1077,7 @@ int net_client_init(QemuOpts *opts, int is_netdev, Error **errp)
     }
 
     error_propagate(errp, err);
+    opts_visitor_cleanup(ov);
     return ret;
 }