Update Dockerfile to use Go version 1.8.3
We require Go version 1.8 since 9.3. We won't be able to use Dockerfile without and CI won't work because of Gitaly build failure.
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
We require Go version 1.8 since 9.3. We won't be able to use Dockerfile without and CI won't work because of Gitaly build failure.
changed milestone to %9.3
mentioned in merge request !307 (merged)