Miss availability zone option when deploy storage backend for cinder

[zhaoleilc]

Description
 ===========
 When we deploy glance storage backend for cinder, there are some options which can
 be set:https://docs.openstack.org/mitaka/config-reference/image-service/backends.html#glance-cinder

 However, there is not an option which is indicative of availability zone.

 When we create an image, a volume is built. We can choose a specific volume type
 by setting cinder_volume_type so that the built volume complies with the specific
 volume type.

 When there is only a availability zone, the built volume is in this availability
 zone and belongs to the specific volume type.
 When there are multiple availability zones, the built volume is in the default
 availability zone, and in that case cinder will report an error which is "No valid
 backend was found" if the specific volume type does not correspond the volume
 backend which belogs to the default availability zone.

 Steps to reproduce
 ==================
 1. Deploy glance storage backend for cinder and set the cinder_volume_type to
 volume_for_glance.
 2. Create the volume type whose name is cinder_volume_type and which does not
 comply with the default availability zone.
 3. Upload a image to glance, but cinder will report an error which is "No valid
 backend was found".
 ​
 Expected result
 ===============
 When we choose a specific volume type by setting cinder_volume_type, the specific
 volume type should be allowed to belong any availability zone.

 Actual result
 =============
 When we choose a specific volume type by setting cinder_volume_type, the specific
 volume type can only belong the default availability zone.
 ​
 Environment
 ===========
 Rocky version of OpenStack