Update to newer OS images for install testing #2136

Job	Run time
build / Build	6m 27s
Integration Tests (certrotation)	1m 38s
Integration Tests (etcdrestore)	1m 56s
Integration Tests (localstorage)	1m 26s
Integration Tests (startup)	7m 57s
Integration Tests (custometcdargs)	42s
Integration Tests (etcdsnapshot)	8m 0s
Integration Tests (kubeflags)	6m 58s
Integration Tests (longhorn)	3m 10s
Integration Tests (secretsencryption)	1m 58s
Integration Tests (flannelnone)	1m 26s
	41m 38s

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