[SRU][regression] get_usage_info fails with OSError class not found, raised on ocata.

[Jorge Niedbalski]

[Description]

Fix for LP: #1698786 backported https://review.openstack.org/625965
into ocata, but python-rbd versions lower than 12.0.3 lacks the specific OSError exception.

var/log/cinder/cinder-volume.log:20:2020-03-05 06:25:22.514 1207092 ERROR oslo_service.service File "/usr/lib/python2.7/dist-packages/cinder/volume/drivers/rbd.py", line 474, in _update_volume_stats
var/log/cinder/cinder-volume.log:21:2020-03-05 06:25:22.514 1207092 ERROR oslo_service.service total_gbi = self._get_usage_info()
var/log/cinder/cinder-volume.log:22:2020-03-05 06:25:22.514 1207092 ERROR oslo_service.service File "/usr/lib/python2.7/dist-packages/cinder/volume/drivers/rbd.py", line 386, in _get_usage_info
var/log/cinder/cinder-volume.log:23:2020-03-05 06:25:22.514 1207092 ERROR oslo_service.service except (self.rbd.ImageNotFound, self.rbd.OSError):
var/log/cinder/cinder-volume.log:24:2020-03-05 06:25:22.514 1207092 ERROR oslo_service.service AttributeError: 'module' object has no attribute 'OSError'

[Proposed solution]

* Revert -updates
* Implement a new fix that makes use of the class IOError (https://github.com/ceph/ceph/blob/master/src/pybind/rbd/rbd.pyx#L854), that is also available on 10.2.11 (https://github.com/ceph/ceph/blob/v10.2.11/src/pybind/rbd/rbd.pyx#L335)

[Corey Bryant (corey.bryant)]

Reverted in cinder 2:10.0.8-0ubuntu1~cloud3