AIAP: Switch to a readiness probe for the docker and libvirt containers

[ian-howell]

Problem description (if applicable)
The artifact-setup and infra-builder containers are using a naive approach of simply sleeping for 30 seconds, with the expectation that the libvirt and docker services will become available in that time before they begin execution:

• airshipctl/tools/airship-in-a-pod/artifact-setup/assets/entrypoint.sh

  Lines 38 to 39 in 362cc4b

  	printf "Waiting 30 seconds for the libvirt and docker services to be ready\n"
  	sleep 30

• airshipctl/tools/airship-in-a-pod/infra-builder/assets/entrypoint.sh

  Lines 17 to 18 in 362cc4b

  	printf "Waiting 30 seconds for the libvirt and docker services to be ready\n"
  	sleep 30

Proposed change
Modify the base AIAP PodSpec to use readiness probes so the above containers can be sure the services are available. This will prevent errors in the case where the services take a long time to come up while also providing a potential speed boost when they come up very quickly.

[ian-howell]

After thinking about this for a minute, a readiness probe may not be the exact mechanism for this task. However, it would still be nice to have a more intelligent waiting mechanism than sleep

[sirajyasin]

I can start working on this issue.

[sreejithpunnapuzha]

@sirajyasin all yours