Optionally avoid sleeping in `entrypoint.sh`

[zeeke]

Container image might be used as initcontainers in kubernetes Pods. In such scenarios, it's important for the image entrypoint to exits once the copy logic is completed. Otherwise, the pod would stuck in a PodInitializing phase.

Add Makefile rule image-test to check the integrity of the entrypoint.sh script.

https://kubernetes.io/docs/concepts/workloads/pods/init-containers/

refs:

• https://github.com/k8snetworkplumbingwg/sriov-network-operator/pull/581

[coveralls]

Pull Request Test Coverage Report for Build 7802222930

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 45.959%

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Totals
Change from base Build 7076950983:	0.0%
Covered Lines:	563
Relevant Lines:	1225

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💛 - Coveralls