Improve the local.conf sample

This patch adds a workaround for the image volume cache issue[1]
in Cinder to the local.conf sample.
The above workaround has already been added to the Zuul environment.

[1] https://bugs.launchpad.net/cinder/+bug/1953704

Change-Id: I46f2ad99c2d524c60402af48a038434a547f684a

.zuul.yaml

@@ -125,6 +125,8 @@
             $NEUTRON_DHCP_CONF:
               DEFAULT:
                 enable_isolated_metadata: True
+            # NOTE: workaround for Cinder image volume cache problem.
+            # https://bugs.launchpad.net/cinder/+bug/1953704
             $CINDER_CONF:
               lvmdriver-1:
                 image_volume_cache_enabled: False

devstack/local.conf.example

@@ -62,3 +62,9 @@ disable_service tempest
 [[post-config|/etc/neutron/dhcp_agent.ini]]
 [DEFAULT]
 enable_isolated_metadata = True
+
+# NOTE: workaround for Cinder image volume cache problem.
+# https://bugs.launchpad.net/cinder/+bug/1953704
+[[post-config|/etc/cinder/cinder.conf]]
+[lvmdriver-1]
+image_volume_cache_enabled = False

devstack/local.conf.kubernetes

@@ -84,3 +84,9 @@ enable_isolated_metadata = True
 [[post-config|$OCTAVIA_CONF]]
 [controller_worker]
 amp_active_retries=9999
+
+# NOTE: workaround for Cinder image volume cache problem.
+# https://bugs.launchpad.net/cinder/+bug/1953704
+[[post-config|/etc/cinder/cinder.conf]]
+[lvmdriver-1]
+image_volume_cache_enabled = False