Remove Support for Deprecated SSLv3

[alrs]

The Go authors deprecated support for SSLv3 in go 1.13. They've decided to remove it in go 1.14, and have already merged the commit.

See: https://golang.org/issue/32716

This PR, or something like it, should probably land before February 2020.

[elasticmachine]

Since this is a community submitted pull request, a Jenkins build has not been kicked off automatically. Can an Elastic organization member please verify the contents of this patch and then kick off a build manually?

[elasticmachine]

Since this is a community submitted pull request, a Jenkins build has not been kicked off automatically. Can an Elastic organization member please verify the contents of this patch and then kick off a build manually?

[urso]

@faec please have a look. For now lets add a deprecation warning if older versions are configured.

[mergify]

This pull request is now in conflicts. Could you fix it? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

git fetch upstream
git checkout -b remove-deprecated-SSLv3 upstream/remove-deprecated-SSLv3
git merge upstream/master
git push upstream remove-deprecated-SSLv3

[mergify]

This pull request does not have a backport label. Could you fix it @alrs? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-v./d./d./d is the label to automatically backport to the 7./d branch. /d is the digit

NOTE: backport-skip has been added to this pull request.

[elasticmachine]

Pinging @elastic/elastic-agent-data-plane (Team:Elastic-Agent-Data-Plane)

[jlind23]

@faec @rdner can we have your eyes on this?

[faec]

Closing this version -- it was out of sync and missed a number of occurrences (including in the docs), but a more complete version was just checked in.