virtio-net: increase defaults rx|tx-queue-size to 1024

virtio-net: increase defaults rx|tx-queue-size to 1024

This is reducing packet drop on high pps, and also needed for dpdk.

Redhat already have use it by default in rhev and his openstack platform too
since 2019.

I'm using it in production since 6 months, I don't have seen performance regression.

fix: (which ask for custom option, but setting it by default seem fine for me)

https://bugzilla.proxmox.com/show_bug.cgi?id=1546
https://bugzilla.proxmox.com/show_bug.cgi?id=2349
Signed-off-by: Alexandre Derumier <aderumier@odiso.com>