Fix volume_driver configuration < ocata

For releases prior to ocata, the volume_driver key must be
provided by the CephContext to ensure that a single driver
is set for cinder.

Specialize behaviour for >= ocata only, resolving issues with
pre ocata deployments with direct relations to ceph.

Change-Id: I9ff47853ab0726ed5c77c67f21f873349bc64f7b

hooks/cinder_contexts.py

@@ -70,8 +70,12 @@ class CephContext(OSContextGenerator):
             volume_driver = 'cinder.volume.drivers.rbd.RBDDriver'
         else:
             volume_driver = 'cinder.volume.driver.RBDDriver'
+        if os_release('cinder-common') >= "ocata":
+            driver_key = 'ceph_volume_driver'
+        else:
+            driver_key = 'volume_driver'
         return {
-            'ceph_volume_driver': volume_driver,
+            driver_key: volume_driver,
             # ensure_ceph_pool() creates pool based on service name.
             'rbd_pool': service,
             'rbd_user': service,

unit_tests/test_cinder_contexts.py

@@ -75,7 +75,7 @@ class TestCinderContext(CharmTestCase):
         self.service_name.return_value = service
         self.assertEquals(
             contexts.CephContext()(),
-            {'ceph_volume_driver': 'cinder.volume.driver.RBDDriver',
+            {'volume_driver': 'cinder.volume.driver.RBDDriver',
              'rbd_pool': service,
              'rbd_user': service,
              'host': service})
@@ -85,6 +85,18 @@ class TestCinderContext(CharmTestCase):
         self.os_release.return_value = 'icehouse'
         service = 'mycinder'
         self.service_name.return_value = service
+        self.assertEquals(
+            contexts.CephContext()(),
+            {'volume_driver': 'cinder.volume.drivers.rbd.RBDDriver',
+             'rbd_pool': service,
+             'rbd_user': service,
+             'host': service})
+
+    def test_ceph_related_ocata(self):
+        self.relation_ids.return_value = ['ceph:0']
+        self.os_release.return_value = 'ocata'
+        service = 'mycinder'
+        self.service_name.return_value = service
         self.assertEquals(
             contexts.CephContext()(),
             {'ceph_volume_driver': 'cinder.volume.drivers.rbd.RBDDriver',