test: fix Azure Stack E2E cluster provisioner

[haofan-ms]

Reason for Change:

• E2E test for kube-proxy version validation failed for k8s 1.15 as the hyperkube image for Azure Stack have a different suffix
• E2E test for akse 0.48.0 upgrade scenario on Azure Stack hit certificate issue as python -v command didn't return the expected information for python 2

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 #3874 into master will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #3874   +/-   ##
=======================================
  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
cmd/scale.go	12.63% <ø> (ø)
cmd/addpool.go	18.07% <100.00%> (ø)
cmd/deploy.go	60.59% <100.00%> (ø)
pkg/api/vlabs/validate.go	78.92% <100.00%> (+0.03%)	⬆️

---

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[jadarsie]

lgtm

[jackfrancis]

/lgtm

[acs-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: haofan-ms, jackfrancis

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