Scheduling jobs in transactions can lead to race conditions where a job
runs before a transaction has been committed. The added initializer
ensures the various Sidekiq scheduling methods raise an error when
called inside a transaction.

Fixes #27233

Update session cookie key name to be unique to instance in development

Closes #31644

See merge request !11839

Fix https://gitlab.com/gitlab-org/gitlab-ce/issues/31644

Resolve N+1 query issue with discussions

Closes #33013

See merge request !11775

* upstream/master: (116 commits)
  Revert "Merge branch 'grpc-1.3.4' into 'master'"
  Return nil when looking up config for unknown LDAP provider
  Avoid crash when trying to parse string with invalid UTF-8 sequence
  Enable Gitaly by default in GitLab 9.3
  Don’t create comment on JIRA if link already exists
  Disable sub_group_issuables_spec.rb for mysql
  Fix math rendering on blob pages
  Add changelog
  Don't allow to pass a user to ProjectWiki#http_url_to_repo
  Revert "Merge branch '1937-https-clone-url-username' into 'master'
"
  Fix bottom padding for build page
  Fix /unsubscribe slash command creating extra todos
  Fix omniauth-google-oauth2 dependencies in Gemfile.lock
  Update looks job log
  'New issue'/'New merge request' dropdowns should show only projects with issues/merge requests feature enabled
  Fix spec for Members::AuthorizedDestroyService
  31616-add-uptime-of-gitlab-instance-in-admin-area
  Set head pipeline when creating merge requests
  Create a separate helper to check if we show particular tab on a search page
  Add performance deltas between app deployments on Merge Request widget
  ...

Enable Gitaly by default in GitLab 9.3

Closes gitaly#242

See merge request !11796