Use handler status if extension status is None when computing the Ext…

[dhivyaganesan]

…… (#2358)

• Use handler status if extension status is None when computing the ExtensionsSummary

• Add NotReady to convergence statuses

Co-authored-by: narrieta
(cherry picked from commit 81f7a1d)

Description

Issue #

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PR information

• The title of the PR is clear and informative.
• There are a small number of commits, each of which has an informative message. This means that previously merged commits do not appear in the history of the PR. For information on cleaning up the commits in your pull request, see this page.
• If applicable, the PR references the bug/issue that it fixes in the description.
• New Unit tests were added for the changes made

Quality of Code and Contribution Guidelines

• I have read the contribution guidelines.

[codecov]

Codecov Report

Merging #2361 (2c66847) into develop (66c894e) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff            @@
##           develop    #2361   +/-   ##
========================================
  Coverage    70.86%   70.87%           
========================================
  Files           97       97           
  Lines        14090    14093    +3     
  Branches      2029     2029           
========================================
+ Hits          9985     9988    +3     
  Misses        3656     3656           
  Partials       449      449           

Impacted Files	Coverage Δ
azurelinuxagent/ga/exthandlers.py	86.22% <100.00%> (+0.03%)	⬆️
azurelinuxagent/ga/update.py	88.22% <100.00%> (ø)

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