neutron-sriov-agent consumes much resources by redundand calls to ip link show

snippets are taken on snapshot #688

This should be significantly improved by the following upstream patch: https://review.openstack.org/416400

Can someone cherry-pick this change and confirm the fix? https://review.openstack.org/#/c/416523/1

Grab the latest version from https://review.openstack.org/#/c/416523 , not the first one in the series.

Proposed cherry-pick here so we don't have to wait for upstream: https://review.fuel-infra.org/29676

Fix https://review.openstack.org/#/c/416524/ was merged in upstream for stable/mitaka. Waiting for regular sync.

stable/mitaka sync in downstream https://review.fuel-infra.org/#/c/29701/

Reviewed: https://review.fuel-infra.org/29701
Submitter: Pkgs Jenkins <email address hidden>
Branch: 9.0/mitaka

Commit: 38f448751c553098539b787e755b6688dcdf59bf
Author: Jenkins <email address hidden>
Date: Tue Jan 10 12:12:06 2017

Merge the tip of origin/stable/mitaka into origin/9.0/mitaka

67e334b Reduce IP link show calls for SR-IOV scan loop

Closes-Bug: #1653131
Change-Id: I9c8ca8fb807836de944bf845ef9928135f82400a

Change abandoned by Alexander Ignatov <email address hidden> on branch: 9.0/mitaka
Review: https://review.fuel-infra.org/29676
Reason: Abandoning in favor of https://review.fuel-infra.org/#/c/29701/

Fixed by https://review.fuel-infra.org/#/c/28335/ in 10.0/newton

Verified on 9.2 snap 822

root@node-3:~# grep '12:07:' /var/log/neutron/neutron-sriov-agent.log | grep "'ip', 'link', 'show'" | wc -l
30
root@node-3:~# vim /var/log/neutron/neutron-sriov-agent.log
root@node-3:~# grep '11:03:' /var/log/neutron/neutron-sriov-agent.log | grep "'ip', 'link', 'show'" | wc -l
15
root@node-3:~# ip link show | grep '^[0-9].*' | wc -l
25
root@node-3:~# ip link show | grep '^[0-9].*' | wc ^C
root@node-3:~# ip link show | grep '^[0-9].*' | grep eth | wc -l
8
root@node-3:~# grep '11:04:' /var/log/neutron/neutron-sriov-agent.log | grep "'ip', 'link', 'show'" | wc -l
30