Machine deployment scale fails after v1alpha3 -> v1alpha4,v1beta1 upgrade

[shysank]

/kind bug

What steps did you take and what happened:

1. create v1alpha3 cluster with v1alpha3 providers
2. upgrade providers to v1beta1
3. scale md to 2
4. capi reconciliation fails with validation error in AzureMachineTemplate

What did you expect to happen:
machine deployment should scale to 2

Anything else you would like to add:
This is because we added new default webhooks in azure machine template which were not there in v1alpha3. When capi tries to update owner references for infrastructure reference (azuremachinetemplate), it applies the default webhooks, specifically, it sets osdisk.CachingType = None, but the default webhooks are not applied for the old spec. So, validateUpdate fails because we check for immutability.

Environment:

• cluster-api-provider-azure version:
• Kubernetes version: (use kubectl version):
• OS (e.g. from /etc/os-release):

[shysank]

/priority important-soon

[shysank]

I verified this by printing old and new specs in validation webhooks:

OLD SPEC = {<nil> Standard_D2s_v3 <nil> <nil> None []  {Linux 0xc000f2180c 0xc000fa4048 <nil> } [] 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 map[] false false <nil> <nil> <nil> }

NEW SPEC = {<nil> Standard_D2s_v3 <nil> <nil> None []  {Linux 0xc000f21730 0xc000fa4030 <nil> None} [] 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 map[] false false <nil> <nil> <nil> }

[CecileRobertMichon]

Thanks for catching this @shysank. Looking forward to having CI tests for this.

[shysank]

Closing this as this is fixed in #1771 and #1824