Refactor project_members_controller_spec
Make tests more readable, DRY and closer to RSpec best practices.
Same as https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6985 but for project_members_controller_spec now
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
Make tests more readable, DRY and closer to RSpec best practices.
Same as https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6985 but for project_members_controller_spec now