Fix the specs to work with canceling status

- Add spec for supports_canceling?
- Fix pipeline feature spec and add an example
- Fix merge train auto merge service spec
- Consider a build retryable if canceling since
users should not need to wait for the after_script
to run to retry
- Fix cancel pipeline service spec
- Fix the cancel redundant pipelines service spec
- Fix create pipeline service spec
- Fix cancel redundant pipelines worker spec
Fix 2 more specs:
- spec/models/environment_spec.rb
- spec/workers/ci/cancel_pipeline_worker_spec.rb