Consolidate test util functions #11005

Job	Run time
build-windows / Build	7m 16s
build / Build	7m 41s
Integration Tests (windows)	2m 1s
Integration Tests (certrotation)	1m 37s
Integration Tests (etcdrestore)	1m 41s
Integration Tests (cacertrotation)	2m 23s
Integration Tests (localstorage)	1m 19s
Integration Tests (kubeflags)	6m 35s
Integration Tests (startup)	7m 21s
Integration Tests (flannelnone)	1m 13s
Integration Tests (secretsencryption)	2m 3s
Integration Tests (custometcdargs)	42s
Integration Tests (etcdsnapshot)	7m 58s
Integration Tests (longhorn)	2m 55s
	52m 45s

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