v6.x backport: test: refactor several parallel/test-timer tests#12401

BethGriggs wants to merge 1 commit intonodejs:v6.x-stagingnodejs/node:v6.x-stagingfrom

BethGriggs:backport-10524-to-v6.xBethGriggs/node:backport-10524-to-v6.xCopy head branch name to clipboard