Adding e2e test for cert renewal with given private key pem file

[pravinpushkar]

Signed-off-by: Pravin Pushkar ppushkar@microsoft.com

Description

1. Parse provided pem encoded file before passing to x509.ParseECPrivateKey
2. e2e tests added for renewing cert with given pem encoded private key file.
3. Added an example-root.key file added in testdata

Issue reference

Related to issue #892

Checklist

Please make sure you've completed the relevant tasks for this PR, out of the following list:

• Code compiles correctly
• Created/updated tests
• Extended the documentation

[codecov]

Codecov Report

Merging #931 (d9afe88) into master (a134860) will decrease coverage by 0.03%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #931      +/-   ##
==========================================
- Coverage   20.49%   20.46%   -0.04%     
==========================================
  Files          32       32              
  Lines        1888     1891       +3     
==========================================
  Hits          387      387              
- Misses       1447     1450       +3     
  Partials       54       54              

Impacted Files	Coverage Δ
pkg/kubernetes/renew_certificate.go	0.00% <0.00%> (ø)

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[mukundansundar]

@yaron2 please review ...