This feature changes Cinder to transfer
snapshots with volumes at the same time by default.
If user doesn't want to transfer snapshots, they could use
a new optional argument '--no-snapshots' after microversion 3.55.
And we also introduce the new V3 api 'v3/volume_transfers'
to move this API out of contrib into Cinder V3 API.
The cinderclient patch: https://review.openstack.org/#/c/577611/
Change-Id: If848d131e5edcdb77d0b3c2ca45a99c4d5e14d1e
Implements: blueprint transfer-snps-with-vols
c0efaa1d46