🏃 Add unit tests for health check function

[chuckha]

Signed-off-by: Chuck Ha [email protected]

This codifies (in tests) the expectations we make around meta health checks.

Here are a list of checks included in this PR:

• When a machine's node was not checked for health. An absence of health from a node is bad.
• The health check returns an error not related to a node's health. For example, the health check cannot connect to the api server to get a list of nodes.
• More nodes than machines were checked. This means there are control plane nodes not managed by cluster api and that is considered unhealthy.
• A machine has a nil node reference. This means the control plane hasn't actually been created or is in the process of being deleted. The control plane cannot be healthy.

cc @dlipovetsky If i'm missing anything you can think of, please let me know!

Somewhat related to #2454

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[chuckha]

@sethp-nr alright, additional cases are covered!

[sethp-nr]

Awesome, thanks Chuck!

/lgtm (though I don't think I have the bit)

[detiber]

/lgtm
@sethp-nr we should probably get you added as a reviewer, then 😁

[chuckha]

@sethp-nr you can /lgtm since you're in the kubernetes-sigs org (i'm like 99% sure)

but you have to put the /lgtm alone on it's own line

[sethp-nr]

@chuckha Oh, I'll have to try it properly next time.

@detiber I certainly wouldn't say no :)