Enabling Auth for Azure-workflow service using Istio.

To enable the authentication via Istio and implement a conditional auth for the service. If istio is required a desired flag azure_istioauth_enabled needs to be true in the env variables and in case aad is required azure_istioauth_enabled is false along with azure.activedirectory.session-stateless : true, azure.activedirectory.client-id : "****" and azure.activedirectory.AppIdUri : 'api://****' need to be passed via the env variables.