Break long poll loop early when context remaining timeout is too low

[vytautas-karpavicius]

What changed? Stop long poll on the client side when too little time is left on the context.

Why? To prevent unnecessary call to the server will would timeout anyway.

Relate Server PR: https://github.com/uber/cadence/pull/4425

How did you test it? Locally.

Potential risks

[coveralls]

Pull Request Test Coverage Report for Build 045dc6fd-ee25-4797-9592-38002509929e

• 5 of 7 (71.43%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.02%) to 71.54%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
internal/internal_workflow_client.go	5	7	71.43%
<!--	Total:	5	7

Totals
Change from base Build 824b8973-99ad-4f10-9ea7-7b04277109c0:	0.02%
Covered Lines:	12174
Relevant Lines:	17017

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💛 - Coveralls