Allow writing 'null' for HardwareRAIDVolumes and SoftwareRAIDVolumes.

[levsha]

BuildRAIDCleanSteps and saveHostProvisioningSettings rely on distinguishing between empty/missing and [].

Not allowing this causes errors like this:

Reconciler error,reconciler group:metal3.io,reconciler kind:BareMetalHost,name:sch05,namespace:cluster-sch,error:failed to save host status after "preparing": BareMetalHost.metal3.io "sch05" is invalid: status.provisioning.raid.hardwareRAIDVolumes: Invalid value: "null": status.provisioning.raid.hardwareRAIDVolumes in body must be of type array: "null",errorVerbose:BareMetalHost.metal3.io "sch05" is invalid: status.provisioning.raid.hardwareRAIDVolumes: Invalid value: "null": status.provisioning.raid.hardwareRAIDVolumes in body must be of type array: "null"
 failed to save host status after "preparing"
 github.com/metal3-io/baremetal-operator/controllers/metal3%2eio.(*BareMetalHostReconciler).Reconcile
 	/workspace/controllers/metal3.io/baremetalhost_controller.go:259
 sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).reconcileHandler
 	/go/pkg/mod/sigs.k8s.io/controller-runtime@v0.9.0/pkg/internal/controller/controller.go:298
 sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).processNextWorkItem
 	/go/pkg/mod/sigs.k8s.io/controller-runtime@v0.9.0/pkg/internal/controller/controller.go:253
 sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Start.func2.2
 	/go/pkg/mod/sigs.k8s.io/controller-runtime@v0.9.0/pkg/internal/controller/controller.go:214
 runtime.goexit
 	/usr/local/go/src/runtime/asm_amd64.s:1371,stacktrace:sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).processNextWorkItem
 	/go/pkg/mod/sigs.k8s.io/controller-runtime@v0.9.0/pkg/internal/controller/controller.go:253
 sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Start.func2.2
 	/go/pkg/mod/sigs.k8s.io/controller-runtime@v0.9.0/pkg/internal/controller/controller.go:214

[metal3-io-bot]

Hi @levsha. Thanks for your PR.

I'm waiting for a metal3-io member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[s3rj1k]

/ok-to-test

[dtantsur]

/test-integration
/lgtm

[hardys]

Should we include something in the docstring which describes that you can set the value to null, and what that means?

[hardys]

I guess this was missed from #942 - it's unfortunate this kind of thing can't be caught via unit tests - I wonder if there's anything we can do in future to get some coverage via the integration tests.

/cc @andfasano

[zaneb]

/approve

[metal3-io-bot]

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This pull-request has been approved by: zaneb

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