Description of problem:
I was unable to delete a quota called 'limit' even in Quota details 'VM', 'Templates' subtabs there is not VM using this quota. But in quota list, i see for 'limit' quota 'Storage Comsumption 90%' -- related to BZ908809?

limit: cf6f0c9d-ba19-4e56-9d6d-15aac59c3426
test:  ec4e34ca-0e86-42a4-a649-6f26d1a65600

$ for i in vms disks ; do curl -sk -X GET -u 'admin@internal:x' -H 'Accept: application/xml' https://10.34.63.76/api/$i ; done | grep quota | sort | uniq
<quota id="00000000-0000-0000-0000-000000000000"/>
<quota id="ec4e34ca-0e86-42a4-a649-6f26d1a65600"/>

While deleting 'limit' quota from Administration Portal.

2013-02-11 11:20:09,940 INFO  [org.ovirt.engine.core.dal.dbbroker.auditloghandling.AuditLogDirector] (QuartzScheduler_Worker-70) No string for UNASSIGNED type. Use default Log
2013-02-11 11:20:16,397 WARN  [org.ovirt.engine.core.bll.RemoveQuotaCommand] (ajp-/127.0.0.1:8702-5) CanDoAction of action RemoveQuota failed. Reasons:VAR__ACTION__REMOVE,VAR__TYPE__QUOTA,ACTION_TYPE_FAILED_QUOTA_IN_USE_BY_VM_OR_DISK

With current UI it is impossible to even detect where could be problem.

Version-Release number of selected component (if applicable):
sf6

How reproducible:
no

Steps to Reproduce:
1.
2.
3.
  
Actual results:
I could not deleted quota, even no VM/disks was using it. I managed to delete it while disabling quota on the DC.

Expected results:
?

Additional info:
I see there's hidden default quota '<quota id="00000000-0000-0000-0000-000000000000"/>', so maybe the trick could be to list this quota as 'Default' with unlimited resources by default. While deleting another quota, all objects could change quota to this 'Default' one, then there would be no untrackable objects using old quota. What is the purpose of keeping old quota internally when the quota is deleted from UI? (I can only think about getting list of objects which used "old/deleted" quota for some "recovery" issue, nevertheless the quota settings were lost anyway.)

If I assign a disk to quota - Storage tab - Add disk, define quota - I cannot see without inspecting api this disk uses any quota. Quota details subpane should contain 'Disks' tab to help with this.