Comment 9 for bug 1782421

I tried to update network revision only when there is an IPAMAloocation change, using revises_on_change in that case network will get a new revision when there is a new IPAMAllocation(ip) , also Subnet model already has revises_on_change for 'network', so when there is a change in subnet it will be handled.

With these changes and above mentione revision_lugin check I am able to achieve 500 VM scale target with 2 VM deploy failed time out errors due to 'standardattributes' update issue.

Also proposed my change here.

https://review.openstack.org/#/c/587373/