Horizon quota collection sub-optimal

[Dmitry Sutyagin]

Confirmed on:
MOS 7.0
MOS 6.0

Issue:
When user accesses `horizon/project/access_and_security/` page, this triggers a call to api/network->tenant_floating_ip_list, and this happens for each tab with preload = True (default) which has any related quotas in table_actions field of the related table.

Details:
For example for keypairs tab it is
table_actions = (CreateKeyPair, ImportKeyPair, DeleteKeyPairs,
                         KeypairsFilterAction,)
Here `CreateKeyPair` will trigger call to quotas.tenant_quota_usages(request) check which will in turn call tenant_floating_ip_list.

On default MOS 7.0 and 6.0 the call to floating_ip_list happens 2 times on this page.
If we set preload = False in https://github.com/openstack/horizon/blob/master/horizon/tabs/base.py#L257 then floating_ip_list is called once, but will also happen for Keypairs tab, and 2 times for FloaitngIPs tab (once for quotas and another time to actually get the IPs).

Current quota retrieval mechanism is suboptimal and should be cached to not duplicate calls for tabs or allow doing calls to get specific quota (for example, only keypair quota or only floatingip quota).

Current code assumes fast/cheap API response which may sometimes not be true - for huge clouds for example.

[Timur Sufiev (tsufiev-x)]

Upstream bug: https://bugs.launchpad.net/horizon/+bug/1512411

[Denis Meltsaykin (dmeltsaykin)]

Setting this as Won't Fix for updates branches as this is predicted behaviour and not a bug. Besides, fixing this bug will break the compatibility.

[Paul Karikh (pkarikh)]

Upstream patch in progress: https://review.openstack.org/#/c/248151/

[Roman Rufanov (rrufanov)]

Customer found on 6.0 - need fix.

[Timur Sufiev (tsufiev-x)]

Given inferior unit-test coverage of Quota subsystem in Horizon, we cannot fix this issue reliably in a remaining week before SCF, thus moving it to 9.0. The plan is first to improve test coverage, then finalize quota calls optimization.

[Alexey Stupnikov (astupnikov)]

Set this bug's status to Won't fix (wontfix-low) since 6.0 is now in Limited support status and only security fixes are accepted.

[Dina Belova (dbelova)]

Won't fix for 9.0 due to medium priority and lots other issues to be fixed. Targeting to 10.0