Fluentd: Add support for arbitrary secret env variables

This adds a helm-toolkit util for consuming arbitrary secret env
variables via pod env variables. It also updates the Fluentd chart
to add a release secret that is used to house the secret env
variables defined in the chart's values.yaml. This can be used as
an example to expand to other charts where this functionality is
desired

Change-Id: I9ef606840af92e54b2204e637c58442085e2c748
Signed-off-by: Steve Wilkerson <sw5822@att.com>

fluentd/values.yaml

@@ -407,7 +407,9 @@ network_policy:
 
 pod:
   env:
-    fluentd: null
+    fluentd:
+      vars: null
+      secrets: null
   tolerations:
     fluentd:
       enabled: false
@@ -489,5 +491,6 @@ manifests:
       service_exporter: true
   network_policy: false
   secret_elasticsearch: true
+  secret_fluentd_env: true
   secret_kafka: false
   service_fluentd: true