Merge branch 'fix-load-balancer-sticking' into 'master'

app/models/ci/runner.rb

app/models/ee/build.rb

app/models/ee/ci/runner.rb

app/services/ee/user_project_access_changed_service.rb

app/services/user_project_access_changed_service.rb

lib/api/helpers.rb

lib/api/helpers/runner.rb

lib/ci/api/helpers.rb

lib/ee/api/helpers.rb

lib/ee/api/helpers/runner.rb

lib/ee/ci/api/helpers.rb

lib/gitlab/database/load_balancing.rb

lib/gitlab/database/load_balancing/connection_proxy.rb

lib/gitlab/database/load_balancing/rack_middleware.rb

lib/gitlab/database/load_balancing/session.rb

lib/gitlab/database/load_balancing/sticking.rb

spec/lib/ee/api/helpers/runner_spec.rb

spec/lib/ee/api/helpers_spec.rb

spec/lib/ee/ci/api/helpers_spec.rb

...b/gitlab/database/load_balancing/connection_proxy_spec.rb