Fix invalid filter passed to list_volumes
Fix invalid filter passed to list_volumes

display_name is not a valid filter for list_volumes, i.e., for non-admin
users no matter what value we set for display_name filter, all volumes
will be returned. We'd better to use name filter for it works all the
time.
https://github.com/openstack/cinder/blob/master/doc/source/admin/generalized_filters.rst

Change-Id: Ib25f4767b74d4494edfafa211d5884a01c1b6488

openstack/tempest,cisco-openstack/tempest,masayukig/tempest,cisco-openstack/tempest,openstack/tempest,masayukig/tempest