Implement nova 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: I740be64fd5d822a4c4718e9b56b9fff34c2ba9da
Related-Prod: PROD-22099
diff --git a/tests/pillar/compute_single.sls b/tests/pillar/compute_single.sls
index 8d752de..b000da7 100644
--- a/tests/pillar/compute_single.sls
+++ b/tests/pillar/compute_single.sls
@@ -60,6 +60,10 @@
       members:
       - host: 127.0.0.1
         port: 11211
+      security:
+        enabled: true
+        strategy: ENCRYPT
+        secret_key: secret
     qemu:
       user: nova
       group: cinder