Add missing security context to elasticsearch pods/containers

This updates the elasticsearch chart to include the pod
security context on the pod template.

This also adds the container security context to set
readOnlyRootFilesystem flag to true

Change-Id: I8d1057f242b741fd297eca7475eb3bfb5e383f1c

elasticsearch/values.yaml

@@ -243,6 +243,24 @@ pod:
               - IPC_LOCK
               - SYS_RESOURCE
           readOnlyRootFilesystem: false
+    curator:
+      pod:
+        runAsUser: 0
+      container:
+        curator:
+          readOnlyRootFilesystem: true
+    verify_repositories:
+      pod:
+        runAsUser: 0
+      container:
+        elasticsearch_verify_repositories:
+          readOnlyRootFilesystem: true
+    create_template:
+      pod:
+        runAsUser: 0
+      container:
+        create_elasticsearch_template:
+          readOnlyRootFilesystem: true
   affinity:
     anti:
       type: