testing multiple iterations for clearing cache #271

Job	Run time
build-versions	3s
build-images (fpm, 8.3) / build-image	1m 22s
build-images (fpm-alpine, 8.3) / build-image	56s
build-images (fpm, 8.2) / build-image	58s
build-images (fpm, 8.1) / build-image	48s
build-images (fpm-alpine, 8.2) / build-image	1m 29s
build-images (fpm-alpine, 8.1) / build-image	1m 1s
build-images (apache, 8.3) / build-image	47s
build-images (apache, 8.2) / build-image	1m 11s
build-images (apache, 8.1) / build-image	1m 10s
latest (apache, 8.3, 8) / build-image	56s
latest (fpm, 8.3, 8) / build-image	1m 6s
latest (fpm-alpine, 8.3, 8) / build-image	1m 20s
clear-cache	3s
	13m 10s

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