Add Azure VM support for add_cloud_metadata processor

[saada]

Closes #3784.
Tests pass locally.
Follows the guidelines here: https://docs.microsoft.com/en-us/azure/virtual-machines/linux/instance-metadata-service

[elasticmachine]

Can one of the admins verify this patch?

[ruflin]

Thanks a lot for this contribution. Could you adda CHANGELOG entry?

[ruflin]

jenkins, test it

[saada]

Thanks @ruflin, where do I add the change log? Under rc1 notes?

[ruflin]

@saada Best add it after - Add support for enabling TLS renegotiation. {issue}4386[4386].

[saada]

@ruflin I don't see that entry in the changelog.

[andrewkroh]

LGTM. Thanks!

[andrewkroh]

@saada Have a look at the raw view of the CHANGELOG file.

[saada]

🎉 Done!

[andrewkroh]

I just thought of one more thing we need with this change. Can you update the add_cloud_metadata docs to include Azure.

[saada]

@andrewkroh done 👍

[ruflin]

jenkins, test it