Use cinderclient to search volume

[hongbin]

The "search_volume" in zun.volume.cinder_api [1] is a re-implementation of "find" in cinderclient [2]. It is better to re-use the implementation in cinderclient instead of re-implementing our own. Let's investigate if we can leverage "find" to implement "search_volume" so that we can reduce the codes to maintain.

[1] https://github.com/openstack/zun/blob/master/zun/volume/cinder_api.py
[2] https://github.com/openstack/python-cinderclient/blob/master/cinderclient/base.py#L368

[hongbin (hongbin034)]

Fixed in: https://review.openstack.org/#/c/521478/