Merge branch '29056-backport-ee-cleanup-database-file' into 'master'

...gs/unreleased/29056-backport-ee-cleanup-database-file.yml

...igrate/20130218141258_convert_closed_to_state_in_issue.rb

...0130218141327_convert_closed_to_state_in_merge_request.rb

...te/20130218141344_convert_closed_to_state_in_milestone.rb

db/migrate/20130315124931_user_color_scheme.rb

...igrate/20131112220935_add_visibility_level_to_projects.rb

...grate/20140313092127_migrate_already_imported_projects.rb

db/migrate/20141007100818_add_visibility_level_to_snippet.rb

db/migrate/20151209144329_migrate_ci_web_hooks.rb

db/migrate/20151209145909_migrate_ci_emails.rb

db/migrate/20151210125232_migrate_ci_slack_service.rb

db/migrate/20151210125927_migrate_ci_hip_chat_service.rb

...20170301205640_migrate_build_events_to_pipeline_events.rb

lib/gitlab/database.rb

lib/gitlab/database/migration_helpers.rb

spec/lib/gitlab/database/migration_helpers_spec.rb

spec/lib/gitlab/database_spec.rb