Implement cinder memcache security strategy

Provides an option to authenticate and optionally encrypt the token
data stored in the cache:
memcache_security_strategy = MAC/ENCRYPT
memcache_secret_key = secret_key

Change-Id: I06dc593e930992291147614d111aa8c34d9f7ee5
Related-Prod: PROD-22099
diff --git a/tests/pillar/volume_single.sls b/tests/pillar/volume_single.sls
index d243510..9ab908c 100644
--- a/tests/pillar/volume_single.sls
+++ b/tests/pillar/volume_single.sls
@@ -45,6 +45,15 @@
       port: 22
       user: username
       password: pass
+    cache:
+      engine: memcached
+      members:
+      - host: 127.0.0.1
+        port: 11211
+      security:
+        enabled: true
+        strategy: ENCRYPT
+        secret_key: secret
 apache:
   server:
     enabled: true