bug 1709729 enabling feature gates for machinehealthchecks

[kalexand-rh]

https://bugzilla.redhat.com/show_bug.cgi?id=1709729

@mburke5678, I broke one of your assemblies in half. If you're not ok with the changes I'm proposing, I can revert them.

@sunzhaohua2, will you PTAL?

preview build: http://file.rdu.redhat.com/kalexand/051419/BZ1709729/machine_management/deploying-machine-health-checks.html

[mburke5678]

@kalexand-rh Why would Disabling Feature Gates not follow Enabling in the same topic?

[kalexand-rh]

@mburke5678, they're different user goals, so they should be different assemblies. This would be like putting installing and uninstalling in the same assembly - you do them at different times for different reasons.

[sunzhaohua2]

@kalexand-rh I think different features have different FeatureGate name, for machinehealthcheck it is machine-api. We should point this out to know how to enable machinehealthcheck.

apiVersion: config.openshift.io/v1
kind: FeatureGate
metadata:
  name: machine-api
spec:
  featureSet: "TechPreviewNoUpgrade"

$ oc get featuregate
NAME          AGE
cluster       45h
machine-api   18h

[kalexand-rh]

#14293 (comment) makes it sound like all of the tech preview features are supposed to be controlled by the same gate.

@enxebre, @ingvagabund, @rphillips, will you confirm that the machinehealthcheck should be controlled by a separate feature gate than the rest of the TP features?

[ingvagabund]

@kalexand-rh at the time of feature gating machinehealthcheck I was not aware all the extra features needs to gated by a specific cluster feature gate. Though, based on #14853 (comment) it looks like there is one.

[ingvagabund]

Addressing our case in openshift/machine-api-operator#318 (hoping it will get merged).

[kalexand-rh]

Jan's PR got merged, and Zhaohua Sun approved the change on the bug. Merging.