feat: S3 add an option to enable/disable "Expect: 100-continue" headers

[ThomasVille]

Since #437, when using Riak-CS v2.1.1 as backend, uploading files larger than 1MB using streams on NodeJS leads to corrupted data stored in Riak-CS.

This PR adds an option to prevent the Expect: 100-continue header from being added to the content of the file when uploading a large file.

Fixes basho/riak_cs#1327.

Checklist

• npm run test passes
• .d.ts file is updated
• changelog is added, npm run add-change

[ThomasVille]

The tests fail with the following error which doesn't seem related to the changes introduced in this PR:

> node ./scripts/region-checker/index.js
Hard-coded regions detected. This should only be done if absolutely certain!
File: /config.js	Line 183:	*     accessKeyId: 'AKID', secretAccessKey: 'SECRET', region: 'us-west-2'
File: /services/s3.js	Line 525:	region = 'us-east-1';
File: /services/s3.js	Line 527:	region = 'eu-west-1';
File: /services/s3.js	Line 646:	request.httpRequest.region === 'us-east-1') {
File: /services/s3.js	Line 657:	service.updateReqBucketRegion(request, 'us-east-1');
File: /services/s3.js	Line 658:	if (bucketRegionCache[bucket] !== 'us-east-1') {
File: /services/s3.js	Line 659:	bucketRegionCache[bucket] = 'us-east-1';
File: /services/s3.js	Line 664:	service.updateReqBucketRegion(getRegionReq, 'us-east-1');
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! aws-sdk@2.498.0 region-check: `node ./scripts/region-checker/index.js`
npm ERR! Exit status 1
npm ERR! 
npm ERR! Failed at the aws-sdk@2.498.0 region-check script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
npm ERR! A complete log of this run can be found in:
npm ERR!     /home/travis/.npm/_logs/2019-07-24T09_01_46_528Z-debug.log

[ThomasVille]

@trivikr Do you have any idea on why the tests fail even though I have not changed anything related to regions in my PR?

[nullren]

@ThomasVille there's a whitelist you need to update in scripts/region-checker/whitelist.js. for example, see e74bd88

[codecov-io]

Codecov Report

Merging #2783 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #2783      +/-   ##
==========================================
+ Coverage   96.96%   96.96%   +<.01%     
==========================================
  Files         300      300              
  Lines        8991     8994       +3     
  Branches     1676     1677       +1     
==========================================
+ Hits         8718     8721       +3     
  Misses        273      273

Impacted Files	Coverage Δ
lib/config.js	87.64% <ø> (ø)	⬆️
lib/services/s3.js	98.19% <100%> (+0.01%)	⬆️

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[ThomasVille]

@nullren Thank you for the hint, I had no idea there was such a whitelist of lines to ignore.

[ajredniwja]

Is this still an active PR? Can the conflicts be merged?