fix(vault): avoid nested variable for id_token

mentioned in commit b965df72

mentioned in merge request to-be-continuous/samples/maven-on-openshift!99

mentioned in merge request to-be-continuous/samples/maven-on-gcloud!163 (merged)

mentioned in merge request to-be-continuous/samples/maven-on-kubernetes!155

mentioned in merge request to-be-continuous/samples/maven-library!58 (merged)

mentioned in merge request d3269/tbc-cicd-for-java!18