Updated openstack/openstack
Project: openstack/python-novaclient  939cf46efee6913fc361e827640d708dbd497747

Change help message for volume-update

`nova volume-update <server> <volume> <volume>` to
`nova volume-update <server> <attachment> <volume>`

Change-Id: Ie820843c3e8d23659075c1d6b4fdd47f639b3b58
Closes-bug: 1326613