Set manage_volume_ref and manage_snapshot_ref

Set manage_volume_ref and manage_snapshot_ref

Ceph doesn't conform with the LVM driver and asks for modifying the
manage volume and snapshop refs [1].

It allows passing test_unmanage_manage_snapshot [2].

[1] https://opendev.org/openstack/tempest/commit/ebc752b59dd3e2164807930e31b313a92bce70d5
[2] http://artifacts.opnfv.org/functest/functest-opnfv-functest-smoke-latest-tempest_full-run-480/tempest_full/tempest-report.html

Change-Id: I8d3b2484ba5cbd203c32fa446fa27e17a80888d5
Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>