test: move cluster tests to parallel
Two cluster tests have recently changed so that they are no longer resource intensive. Move them back to parallel.
Ref: https://github.com/nodejs/node/pull/4736 Ref: https://github.com/nodejs/node/pull/4739
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
Two cluster tests have recently changed so that they are no longer resource intensive. Move them back to parallel.
Ref: https://github.com/nodejs/node/pull/4736 Ref: https://github.com/nodejs/node/pull/4739