Cinder currently has the ability to take over the management of
existing volumes and snapshots ("manage existing") and to relinquish
management of volumes and snapshots ("unmanage"). The API to manage an
existing volume takes a reference, which is a driver-specific string
that is used to identify the volume on the storage backend. This
patch adds the client code for APIs for listing volumes and snapshots
available for management to make this flow more user-friendly.
Change-Id: Icd81a77294d9190ac6dbaa7e7d35e4dedf45e49f
Implements: blueprint list-manage-existing
d24ba31afa