Stop kubelet before update and reboot faster

[PatrickLang]

What this PR does / why we need it:

If you're creating a cluster as part of a test pass - the nodes appear to be ready before any patches are installed. This change will stop the kubelet so the node is not "ready", and also reboot faster. Once the reboot happens - the kubelet will be running and the testing can commence.

cc @adelina-t

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[codecov]

Codecov Report

Merging #4107 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #4107   +/-   ##
=======================================
  Coverage   55.44%   55.44%           
=======================================
  Files         109      109           
  Lines       16056    16056           
=======================================
  Hits         8903     8903           
  Misses       6369     6369           
  Partials      784      784

[PatrickLang]

This was failing until #4119 & #4141 merged. Retesting now

[PatrickLang]

@adelina-t @dineshgovindasamy - I added the workaround to remove the Azure CNI lock after reboot. Can you review?

[PatrickLang]

/hold

The scheduled task still doesn't run after reboot. If you run Get-ScheduledTask -TaskName "RemoveLock" | Start-ScheduledTask it will complete, but it never starts automatically. Need to dig more into this.

[CecileRobertMichon]

@PatrickLang can you please move this to https://github.com/Azure/aks-engine?