Consolidate test util functions #11006

Job	Run time
build / Build	7m 58s
build-windows / Build	7m 37s
Integration Tests (windows)	1m 39s
Integration Tests (startup)	6m 36s
Integration Tests (cacertrotation)	2m 25s
Integration Tests (certrotation)	1m 42s
Integration Tests (localstorage)	1m 21s
Integration Tests (kubeflags)	6m 39s
Integration Tests (flannelnone)	1m 13s
Integration Tests (etcdsnapshot)	7m 6s
Integration Tests (etcdrestore)	1m 53s
Integration Tests (secretsencryption)	1m 58s
Integration Tests (custometcdargs)	33s
Integration Tests (longhorn)	2m 40s
	51m 20s

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