Fix nil pointer exception when deleting MachinePools

[Jont828]

What type of PR is this?
/kind bug

What this PR does / why we need it: We expect the MachinePool cache to be initialized before getting the ScaleSetSpec. However, we only initialize it in reconcileNormal in azuremachinepool.go, so we have a panic trying to get the ScaleSetSpec for deletion. This fix only sets the fields using cache values if the cache is not nil to allow the spec to be available for deletion.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #4012

Special notes for your reviewer:

• cherry-pick candidate

TODOs:

• squashed commits
• includes documentation
• adds unit tests

Release note:

NONE

[CecileRobertMichon]

Good find! overall lgtm. Looks like there are some leftover debug print/log statements, can you please clean those up for merge?

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: -0.02% ⚠️

Comparison is base (e21844c) 56.59% compared to head (ca7964c) 56.57%.
Report is 8 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4019      +/-   ##
==========================================
- Coverage   56.59%   56.57%   -0.02%     
==========================================
  Files         187      187              
  Lines       19124    19130       +6     
==========================================
  Hits        10823    10823              
- Misses       7671     7676       +5     
- Partials      630      631       +1     

Files Changed	Coverage Δ
azure/scope/machinepool.go	29.18% <0.00%> (-0.21%)	⬇️

... and 3 files with indirect coverage changes

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[Jont828]

Sure thing, just wanted to make sure the tests passed before removing logs!

[nojnhuh]

lgtm aside from one comment.

/cherry-pick release-1.11

[nojnhuh]

/cherry-pick release-1.11

[k8s-infra-cherrypick-robot]

@nojnhuh: once the present PR merges, I will cherry-pick it on top of release-1.11 in a new PR and assign it to you.

In response to this:

/cherry-pick release-1.11

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[mboersma]

Agree, this looks good but for the added log lines.

[nojnhuh]

/lgtm
/approve

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: 3e45c07344e35b8de39f8f4b39918e74d97a5ffa

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: nojnhuh

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [nojnhuh]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[CecileRobertMichon]

/lgtm

[k8s-infra-cherrypick-robot]

@nojnhuh: new pull request created: #4025

In response to this:

/cherry-pick release-1.11

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.