Fix startTime in workflow task refresher

[yycptt]

What changed?

• Fix workflow refresh start time value for scheduling workflow timeout timer

Why?

• Start event time is not the actual start time if the workflow has been reset before.

How did you test it?

• reverted change in unit test to assert the correct behavior

Potential risks

Release notes

Documentation Changes

[coveralls]

Pull Request Test Coverage Report for Build 3914ebc5-47bc-4978-af29-4d1525b6fbf7

• 3 of 4 (75.0%) changed or added relevant lines in 3 files are covered.
• 173 unchanged lines in 14 files lost coverage.
• Overall coverage decreased (-0.1%) to 56.373%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
service/history/historyEngine.go	0	1	0.0%

Files with Coverage Reduction	New Missed Lines	%
service/history/execution/mutable_state_task_refresher.go	1	73.82%
common/persistence/taskManager.go	2	73.12%
common/task/weightedRoundRobinTaskScheduler.go	2	88.6%
service/matching/matcher.go	2	91.46%
common/persistence/nosql/nosqlplugin/cassandra/db.go	6	62.5%
common/persistence/nosql/utils.go	7	0%
common/persistence/persistenceMetricClients.go	8	43.33%
common/persistence/nosql/nosqlExecutionStore.go	9	57.52%
common/persistence/nosql/nosqlplugin/cassandra/gocql/public/client.go	9	33.33%
common/persistence/nosql/nosqlplugin/cassandra/workflow.go	9	49.32%

Totals
Change from base Build e8b91ed5-fcc5-4f47-8e20-71b3a1986d54:	-0.1%
Covered Lines:	79750
Relevant Lines:	141468

---

💛 - Coveralls