[zanata/zanata-server] c2da9b: Add comment on why Async annotation is needed

[GitHub]

  Branch: refs/heads/ZNTA-1166-webhook
  Home:   https://github.com/zanata/zanata-server
  Commit: c2da9bf768e242591b93605645a754cedae7f498
      https://github.com/zanata/zanata-server/commit/c2da9bf768e242591b93605645a754cedae7f498
  Author: Alex Eng <aeng at redhat.com>
  Date:   2016-09-13 (Tue, 13 Sep 2016)

  Changed paths:
    M zanata-war/src/main/java/org/zanata/service/impl/WebhookServiceImpl.java

  Log Message:
  -----------
  Add comment on why Async annotation is needed