Fix EventError argument for logging IOError correctly

[taoyama]

Fix EventError argument for logging IOError correctly

I found IOError is not properly logged when Agent fails to save event.
This patch would fix the issue.

Issue #

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This change is 

[codecov]

Codecov Report

Merging #1506 into develop will decrease coverage by <.01%.
The diff coverage is 0%.

@@             Coverage Diff             @@
##           develop    #1506      +/-   ##
===========================================
- Coverage    60.82%   60.82%   -0.01%     
===========================================
  Files           75       75              
  Lines        10878    10879       +1     
  Branches      1559     1559              
===========================================
  Hits          6617     6617              
- Misses        3946     3947       +1     
  Partials       315      315

Impacted Files	Coverage Δ
azurelinuxagent/common/event.py	80% <0%> (-0.31%)	⬇️

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[taoyama]

Any comment on this?

[vrdmr]

Looks good. Thanks for the change.