cinder volume creation failed because glance round-robin

currently cinder config point to VIP for glance api server which breaks cinder volume creation in a multinode HA configuration.

Here are steps to reproduce it:

1. Add image to glance
    glance image-create --name ubuntu-14.04.4-server --container bare --disk-format iso --file ubuntu-14.04.4-server-amd64.iso
glance image-list
+--------------------------------------+-----------------------+
| ID | Name |
+--------------------------------------+-----------------------+
| 90546163-3b61-455a-93ad-e040fd0be1eb | ubuntu-14.04.4-server |
+--------------------------------------+-----------------------+
2. create cinder volume using glance image just created.
   cinder create --name ubuntu-14.04.4-server-cd-1 --image 90546163-3b61-455a-93ad-e040fd0be1eb 1
   This step should succeed.
| eead3df3-68bd-4ef6-80d6-243d1d623056 | available | ubuntu-14.04.4-server-cd-1 | 1 | - | true | |

3. create another cinder volume using the same image, but different volume name
cinder create --name ubuntu-14.04.4-server-cd-2 --image 90546163-3b61-455a-93ad-e040fd0be1eb 1
| 123bc251-9699-4fcd-a370-5333053b787a | error | | 1 | - | false | |

This step will fail because cinder will try to contact glance API by its configured VIP address and due to round-robin, this request will be redirected to one of controllers, since there is no by default replication of glance images, the server where the request landed will not be able to satisfy it and volume creation operation fails.