Shutdown in separate thread for Logs integration tests in current_thread mode.

[lalitb]

Fixes #
To validate #2583 for logs:

• Reduce the sleep to 2 secs, to ensure that the sleep due the logs export is done during shutdown, and timer expiry.
• Invoke shutdown in separate thread for tokio current_thread mode.

Changes

Please provide a brief description of the changes here.

Merge requirement checklist

• CONTRIBUTING guidelines followed
• Unit tests added/updated (if applicable)
• Appropriate CHANGELOG.md files updated for non-trivial, user-facing changes
• Changes in public API reviewed (if applicable)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.2%. Comparing base (b017c7b) to head (4d17751).
Report is 2 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #2601   +/-   ##
=====================================
  Coverage   79.2%   79.2%           
=====================================
  Files        118     118           
  Lines      22503   22503           
=====================================
  Hits       17829   17829           
  Misses      4674    4674           

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[cijothomas]

lets keep 5 for now throughout.

[cijothomas]

LGTM. Once #2588 lands, we need to assert that shutdown returns expected Ok variant.