Add Unit tests for Frontend API Handler

[timl3136]

What changed?
Add unit tests for RespondDecisionTaskFailed and RespondQueryTaskCompleted methods in frontend api handler

Why?
Improve test coverage

How did you test it?
Unit tests

Potential risks

Release notes

Documentation Changes

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 72.01%. Comparing base (b3e21fa) to head (e57054d).

Additional details and impacted files

see 10 files with indirect coverage changes

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[coveralls]

Pull Request Test Coverage Report for Build 018fef2a-cf8f-43ca-8b6d-218108c1f3d4

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 41 unchanged lines in 14 files lost coverage.
• Overall coverage increased (+0.05%) to 71.383%

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Files with Coverage Reduction	New Missed Lines	%
service/history/task/timer_task_executor_base.go	2	80.21%
common/cache/lru.go	2	93.01%
service/matching/tasklist/task_list_manager.go	2	76.65%
common/task/fifo_task_scheduler.go	2	85.57%
service/frontend/api/handler.go	2	73.55%
service/history/replication/task_processor.go	2	82.76%
service/matching/tasklist/task_reader.go	2	76.66%
service/history/task/transfer_standby_task_executor.go	3	86.73%
service/history/task/task.go	3	84.81%
service/history/queue/timer_queue_processor_base.go	3	77.87%

Totals
Change from base Build 018feeec-d7a4-4bb0-b278-1977f0e4c7ed:	0.05%
Covered Lines:	106330
Relevant Lines:	148957

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💛 - Coveralls