Cinder scheduler failed when thin provisioning support

[yenai]

Use LVM as a cinder backend.
cinder.conf:
[lvmdriver-1]
image_volume_cache_enabled = True
volume_clear = zero
lvm_type = thin
lvm_max_over_subscription_ratio = 2
iscsi_helper = lioadm
volume_group = stack-volumes-lvmdriver-1
volume_driver = cinder.volume.drivers.lvm.LVMVolumeDriver
volume_backend_name = lvmdriver-1

VG info:
[root@yenai ~]# vgs
  VG #PV #LV #SN Attr VSize VFree
  cl 1 2 0 wz--n- <39.00g 0
  stack-volumes-default 1 0 0 wz--n- <10.01g <10.01g
  stack-volumes-lvmdriver-1 1 3 0 wz--n- <10.01g 484.00m

The free capacity of stack-volumes-lvmdriver-1 is less than 10G(about 9.51G).
Then we set lvm_max_over_subscription_ratio is 2.
Now we create 4 volumes:
  cinder create --volume-type lvmdriver-1 5
  cinder create --volume-type lvmdriver-1 5
  cinder create --volume-type lvmdriver-1 5
  cinder create --volume-type lvmdriver-1 3
But the result is only 2 volumes created successfully.

+--------------------------------------+-----------+------+------+-------------+----------+-------------+
| ID | Status | Name | Size | Volume Type | Bootable | Attached to |
+--------------------------------------+-----------+------+------+-------------+----------+-------------+
| 7aa9fcd7-7f9f-4e87-9c6d-b6f2923fa3cf | available | - | 5 | lvmdriver-1 | false | |
| 84a457e8-b8d2-4733-9d8b-662d38264f0d | error | - | 5 | lvmdriver-1 | false | |
| 90464fd3-6c62-47a1-8174-4d5174a1de24 | error | - | 3 | lvmdriver-1 | false | |
| e67d36bf-0343-4c1e-ad97-afb03444808d | available | - | 5 | lvmdriver-1 | false | |
+--------------------------------------+-----------+------+------+-------------+----------+-------------+

The attachment is log file for detail.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/507325

[OpenStack Infra (hudson-openstack)]

Change abandoned by yenai (<email address hidden>) on branch: master
Review: https://review.openstack.org/507325
Reason: https://review.openstack.org/#/c/484354/
is the same case.