Change pipeline status to canceled

The PipelineCancel mutation was canceling the jobs in the pipeline, but
not marking the pipeline itself as canceled. This commit fixes that

Changelog: fixed

app/graphql/mutations/ci/pipeline/cancel.rb

@@ -13,6 +13,8 @@ module Mutations
 
           if pipeline.cancelable?
             pipeline.cancel_running
+            pipeline.cancel
+
             { success: true, errors: [] }
           else
             { success: false, errors: ['Pipeline is not cancelable'] }

spec/requests/api/graphql/mutations/ci/pipeline_cancel_spec.rb

@@ -47,5 +47,6 @@ RSpec.describe 'PipelineCancel' do
 
     expect(response).to have_gitlab_http_status(:success)
     expect(build.reload).to be_canceled
+    expect(pipeline.reload).to be_canceled
   end
 end