test: refactor indexOf uses to es6 equivalents
refactor indexOf uses to es6 where applicable
Refs: https://github.com/nodejs/node/issues/12586
#goodnessSquad
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
refactor indexOf uses to es6 where applicable
Refs: https://github.com/nodejs/node/issues/12586
#goodnessSquad