chore: create azure.json via CSE

[jackfrancis]

Reason for Change:

This PR moves the initial creation of /etc/kubernetes/azure.json entirely to CSE. This is to ensure that OS images derived from a running Kubernetes node can be re-used to create new nodes.

tl;dr

• CSE exits 0 immediately if it's already been run
• We don't want cloud-init to blow away stuff that's been mutated by CSE (/etc/kubernetes/azure.json is created by CSE)

See #2849 for the initial implementation of "no azure.json" functionality.

Issue Fixed:

Credit Where Due:

Does this change contain code from or inspired by another project?

• No
• Yes

If "Yes," did you notify that project's maintainers and provide attribution?

• No
• Yes

Requirements:

• uses conventional commit messages
• includes documentation
• adds unit tests
• tested upgrade from previous version

Notes:

[codecov]

Codecov Report

Merging #3876 into master will increase coverage by 0.00%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #3876   +/-   ##
=======================================
  Coverage   72.83%   72.83%           
=======================================
  Files         149      149           
  Lines       23171    23173    +2     
=======================================
+ Hits        16876    16878    +2     
  Misses       5178     5178           
  Partials     1117     1117           

Impacted Files	Coverage Δ
pkg/engine/templates_generated.go	48.65% <ø> (ø)
pkg/api/vlabs/validate.go	78.92% <0.00%> (+0.03%)	⬆️

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[jackfrancis]

cc @Michael-Sinz

[Michael-Sinz]

This fix makes it easier to build a "prototype model" type of VMSS scaling system which should really help scaling speed and reliability. (It was in building the prototype for the "prototype model" that we ran into this issue)

[mboersma]

/lgtm

[acs-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jackfrancis, mboersma

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