Ignore 'lgtm' from the issue owner for Message.approval.
Ignore 'lgtm' from the issue owner for Message.approval.

Review URL: http://codereview.appspot.com/4526091

nicko96/Chrome-Infra,nicko96/Chrome-Infra,nicko96/Chrome-Infra,nicko96/Chrome-Infra,nicko96/Chrome-Infra