disable volume creation, when cinder is disabled

before this patch, it's possible to try to create a volume
from an image, create a volume during instance creation etc.

The same applies to create a volume from snapshot.

Closes-bug: 1267438
(cherry picked from commit 33076684a9db19b5e25ba517ce3ac90bb5c25fc0)

Conflicts:
	openstack_dashboard/dashboards/project/images_and_snapshots/images/tables.py
	openstack_dashboard/dashboards/project/instances/workflows/create_instance.py

Change-Id: Ib573487938e0833668b002d05574e587734ef829
Merge "disable volume creation, when cinder is disabled" into stable/havana