Add -compress-results flag to optionally disable compressing results

[stephen-soltesz]

This change adds a new flag (preserving prior default behavior) to enable or disable compressing ndt7 result files.

After this change, the ndt-server can use -compress-results=false to disable gzip compressed result files, making them jostler/autoloader compatible.

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This change is 

[coveralls]

Pull Request Test Coverage Report for Build 1644

• 25 of 28 (89.29%) changed or added relevant lines in 3 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+0.5%) to 81.948%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
ndt7/results/file.go	19	22	86.36%

Files with Coverage Reduction	New Missed Lines	%
ndt5/c2s/c2s.go	1	74.11%

Totals
Change from base Build 1641:	0.5%
Covered Lines:	1834
Relevant Lines:	2238

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💛 - Coveralls

[robertodauria]

Reviewed 3 of 3 files at r1, all commit messages.
Reviewable status: complete! 1 of 1 approvals obtained