Fix(Impression event): Resolved method post issue

[mnoman09]

Summary

• Checked LogEvent request method type if it is get than generate get request and if it is post than generate post request.

Issues

• failure asserting results[reach][total_count] == expectation.total_impressions
  ERROR:root:expected 1 total visitors; actually found 0 total visitors

[thomaszurkan-optimizely]

LGTM

[coveralls]

Pull Request Test Coverage Report for Build 783

• 2 of 12 (16.67%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.1%) to 89.77%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
core-httpclient-impl/src/main/java/com/optimizely/ab/event/AsyncEventHandler.java	2	12	16.67%

Totals
Change from base Build 779:	-0.1%
Covered Lines:	2694
Relevant Lines:	3001

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💛 - Coveralls