multiqueue vhostuser interface should not have kernel limits applied

[sean mooney]

When multiqueue support was introduced for vhost-user it reuesed the same code to calculate the queue count as kernel vhost.

In https://bugs.launchpad.net/nova/+bug/1570631 and commit https://review.opendev.org/#/c/332660/, a bug was fixed by making the assumption that the kernel version should also dictate the max number of queues on the tap interface when setting hw:vif_multiqueue_enabled=True.

this change did not take account of the fact that this was shared code and incorrectly applied
the hard coded kernel limits to vhost-user interface not just tap devices.

[sean mooney (sean-k-mooney)]

note i have triaged this as low as this is a latent behaviour we have know about for years
however as a bug was filed downstream for this https://bugzilla.redhat.com/show_bug.cgi?id=1714075
i have tagged it against all release back to queens where it was reported.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/700894