Fix memory leak caused by incorrect context deactivation

[shijiesheng]

What changed?
"Scope" the tracing scope so it's closed and removed from thread local storage.

Why?
#895

How did you test it?
unit test + integration test

Potential risks

Release notes

Documentation Changes

[coveralls]

Pull Request Test Coverage Report for Build 2326

Details

• 67 of 69 (97.1%) changed or added relevant lines in 6 files are covered.
• 9 unchanged lines in 4 files lost coverage.
• Overall coverage increased (+0.08%) to 61.521%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/main/java/com/uber/cadence/internal/worker/LocalActivityWorker.java	28	29	96.55%
src/main/java/com/uber/cadence/serviceclient/WorkflowServiceTChannel.java	3	4	75.0%

Files with Coverage Reduction	New Missed Lines	%
src/main/java/com/uber/cadence/internal/replay/ReplayDecisionTaskHandler.java	1	87.8%
src/main/java/com/uber/cadence/internal/worker/Poller.java	1	78.13%
src/main/java/com/uber/cadence/serviceclient/WorkflowServiceTChannel.java	3	11.1%
src/main/java/com/uber/cadence/internal/common/BackoffThrottler.java	4	68.42%

Totals
Change from base Build 2311:	0.08%
Covered Lines:	11975
Relevant Lines:	19465

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💛 - Coveralls