Adjust CINDER_SECURE_DELETE flag to cinder changes

Cater for the pending more general cinder support
for configurable volume wiping method at:
https://review.openstack.org/#/c/12521

This change is done here first so as to not
trigger a CI lockup when the referenced patch above lands.
When that's in place, we can remove the older
secure_delete config adjustment in a subsequent patch.

Change-Id: I73fe2e0d1cf2815ab6025121584951cb5ff56fa3
diff --git a/lib/cinder b/lib/cinder
index 701effd..e3df98a 100644
--- a/lib/cinder
+++ b/lib/cinder
@@ -169,6 +169,7 @@
 
     if [[ "$CINDER_SECURE_DELETE" == "False" ]]; then
         iniset $CINDER_CONF DEFAULT secure_delete False
+        iniset $CINDER_CONF DEFAULT volume_clear none
     fi
 
     if [ "$LOG_COLOR" == "True" ] && [ "$SYSLOG" == "False" ]; then