RFR: 20: Do not send emails that a reviewer has added a comment

[Robin Westberg via github.com]

Hi all,

Please review the following change that stops adding PR comments when a review is updated, if the host supports attaching comments directly to reviews (such as GitHub, but not GitLab CE).

Best regards,
Robin

----------------

Commits:
 - 68dafb3d:	Fix build issue
 - 3850348e:	Skip non-relevant test
 - 4d54d9e1:	Posting a PR comment when a review is found is only useful on GitLab CE

Pull request:
http://git.openjdk.java.net/skara/pull/19

Webrev:
https://openjdk.github.io/cr/skara/19/webrev.00

Patch:
http://git.openjdk.java.net/skara/pull/19.diff

Fetch command:
git fetch https://github.com/openjdk/skara.git 68dafb3d:pr/19