Allow forcing path style for s3 compatible API requests.

[coveralls]

Pull Request Test Coverage Report for Build 60f65f327-PR-745

• 5 of 7 (71.43%) changed or added relevant lines in 1 file are covered.
• 3 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.004%) to 45.628%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
cache/s3/s3.go	5	7	71.43%
<!--	Total:	5	7	71.43%	-->

Files with Coverage Reduction	New Missed Lines	%
server/viewer.go	3	61.54%
<!--	Total:	3		-->

Totals
Change from base Build 7f0e7e660:	0.004%
Covered Lines:	5390
Relevant Lines:	11813

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💛 - Coveralls

[johngian]

I think that this patch fixes #719

[ARolek]

@johngian excellent. Thanks for pointing out that issue.