Rephrase for multiattach support
Rephrase for multiattach support

Since we can enable attaching a volume to multiple servers,
the doc needs update.

Change-Id: Ide7c32f08113392b5f5e0042ec909b41c9cc6f88

mahak/cinder,mahak/cinder,openstack/cinder,phenoxim/cinder,phenoxim/cinder,openstack/cinder