Add keep_alive property to collect_logs

[kevinclark19a]

Description

When stop()ed, the collect logs thread handler goes into loop where the update handler tries to restart it every six seconds and it immediately exits because it is still marked as stopped. This behavior is shared by other sub-classes of ThreadHandlerInterface and might need to be fixed for them as well.

This PR adds a keep alive property to the thread handlers so that the update handler can know whether or not to restart them after they die. One priority in this hotfix was not to change the current behavior of other thread handlers so as to limit the scope of the changes.

[codecov]

Codecov Report

Merging #2533 (7c154d5) into hotfix-2.7.1.0 (76f769c) will decrease coverage by 0.04%.
The diff coverage is 80.00%.

@@                Coverage Diff                 @@
##           hotfix-2.7.1.0    #2533      +/-   ##
==================================================
- Coverage           72.01%   71.96%   -0.05%     
==================================================
  Files                 101      101              
  Lines               15052    15056       +4     
  Branches             2391     2391              
==================================================
- Hits                10839    10835       -4     
- Misses               3732     3736       +4     
- Partials              481      485       +4     

Impacted Files	Coverage Δ
azurelinuxagent/ga/collect_logs.py	80.40% <50.00%> (-0.42%)	⬇️
azurelinuxagent/common/interfaces.py	64.28% <100.00%> (+5.95%)	⬆️
azurelinuxagent/ga/update.py	88.48% <100.00%> (ø)
azurelinuxagent/ga/collect_telemetry_events.py	89.72% <0.00%> (-2.40%)	⬇️

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