Replace display_name by name in scenario manager

'display_name' attribute has been used when calling create_volume
and create_volume_snapshot methods instead of the 'name' which
is the current attribute name based on the current documentation.

[1] https://docs.openstack.org/api-ref/block-storage/v3/
?expanded=create-a-volume-detail#create-a-volume
[2] https://docs.openstack.org/api-ref/block-storage/v3/
?expanded=create-a-snapshot-detail#volume-snapshots-snapshots

Change-Id: Ie22ac7214e77c95ccd03935ffb230241218c08f1
1 file changed