fix: Azure Stack CNI network interfaces file creation fix

[JesusAlvarezTorres]

Reason for Change:

Fixing an issue seen in Azure Stack during the creation of the network interfaces file for the Azure CNI plugin

Issue Fixed:

Requirements:

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

Notes:

[jackfrancis]

lgtm for linux fixes

@marosset and @jsturtevant to review the powershell additions

[jackfrancis]

/azp run pr-e2e

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[codecov]

Codecov Report

Merging #3792 into master will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3792      +/-   ##
==========================================
- Coverage   73.20%   73.20%   -0.01%     
==========================================
  Files         148      148              
  Lines       25384    25428      +44     
==========================================
+ Hits        18582    18614      +32     
- Misses       5666     5679      +13     
+ Partials     1136     1135       -1     

Impacted Files	Coverage Δ
pkg/engine/cse.go	100.00% <ø> (ø)
pkg/engine/templates_generated.go	52.91% <ø> (-0.51%)	⬇️
cmd/upgrade.go	42.71% <0.00%> (-1.50%)	⬇️
pkg/engine/armvariables.go	86.44% <0.00%> (-0.06%)	⬇️
pkg/api/common/const.go	40.00% <0.00%> (ø)
pkg/api/k8s_versions.go	100.00% <0.00%> (ø)
pkg/api/common/versions.go	96.84% <0.00%> (ø)
pkg/api/defaults-kubelet.go	96.82% <0.00%> (+0.01%)	⬆️
pkg/engine/artifacts.go	99.15% <0.00%> (+0.01%)	⬆️
... and 4 more

---

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[jackfrancis]

ping again @marosset @jsturtevant

[JesusAlvarezTorres]

/azp run pr-e2e

[azure-pipelines]

Commenter does not have sufficient privileges for PR 3792 in repo Azure/aks-engine

[jsturtevant]

/azp run pr-e2e

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[marosset]

/lgtm

[acs-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: JesusAlvarezTorres, marosset

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• OWNERS [marosset]

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