fix(@angular/cli): increase keepAliveTimeout for all Node 8 versions

[AmitMY]

Fixes #7197, in continuation to #7563

Thanks @mtraynham for the original fix.

This resolves an issue with browsers throwing net::ERR_CONTENT_LENGTH_MISMATCH for large files or slow connections, when using Webpack Dev Server. Large files, such as a vendor javascript bundle, are susceptible to this bug which is tracked all the way back to the NodeJS http module. A change in NodeJS 8.0 broke the keepAliveTimeout handling where active requests don't reset the timeout timer. This is a proposal fix in NodeJS 8.6, but that is what was last time as well.

The keepAliveTimeout defaults to 5 seconds, which may be too short. This change increases that keepAliveTimeout to 30 seconds, but only if the Node process has versions starting with 8

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[AmitMY]

I signed it!

[googlebot]

CLAs look good, thanks!

[filipesilva]

LGTM, thanks for fixing this 👍

[filipesilva]

Travis is failing on the commit message, can you change it to fix(@angular/cli): increase keepAliveTimeout for all Node 8 versions please?

[AmitMY]

Done. All checks have passed, no idea why travis failed before

[filipesilva]

We have a check for the commit message which makes one of the jobs fail. Your new commit message solved that 👍

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