ITip\Broker: handle timezones in replies to exception events

[gharlan]

fixes #358, closes #360

While rebasing #360, I noticed that it only fixes replies to new exception events. I use a different approach now, which also fixes replies to existing exception events.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.78%. Comparing base (f14092f) to head (bee4fa7).
Report is 6 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #652   +/-   ##
=========================================
  Coverage     98.78%   98.78%           
- Complexity     1866     1868    +2     
=========================================
  Files            71       71           
  Lines          5249     5253    +4     
=========================================
+ Hits           5185     5189    +4     
  Misses           64       64           

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[phil-davis]

LGTM - this solution is cleaner than the original solution from #360

@staabm can you also review please.

[staabm]

I don't see obvious problems