fixes related to a new version of rbfeeder:armhf and some general cleanup #62

Job	Run time
Run hadolint against docker files	6s
Run shellcheck against shell scripts	4s
Test Image Build / Prepare workflow environment	12s
Test Image Build / Build nohealthcheck (linux/arm/v7)	3m 41s
Test Image Build / Build (linux/arm/v7)	3m 48s
Test Image Build / Build (linux/arm64)	3m 44s
Test Image Build / Build (linux/amd64)	1m 13s
Test Image Build / Build (manifest)	4m 46s
Test Image Build / Build nohealthcheck (linux/arm64)	3m 52s
Test Image Build / Build nohealthcheck (manifest)	4m 52s
Test Image Build / Build nohealthcheck (linux/amd64)	1m 1s
	27m 19s

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