Define actions in let so that it could be overridden

Feedback:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/8091/diffs#note_20236356

spec/requests/ci/api/builds_spec.rb

@@ -249,7 +249,13 @@ describe Ci::API::Builds do
     end
 
     describe 'PATCH /builds/:id/trace.txt' do
-      let(:build) { create(:ci_build, :pending, :trace, runner_id: runner.id) }
+      let(:build) do
+        attributes = {runner_id: runner.id, pipeline: pipeline}
+        create(:ci_build, :pending, :trace, attributes) do |build|
+          build.run
+        end
+      end
+
       let(:headers) { { Ci::API::Helpers::BUILD_TOKEN_HEADER => build.token, 'Content-Type' => 'text/plain' } }
       let(:headers_with_range) { headers.merge({ 'Content-Range' => '11-20' }) }
       let(:update_interval) { 10.seconds.to_i }
@@ -276,7 +282,6 @@ describe Ci::API::Builds do
       end
 
       before do
-        build.run!
         initial_patch_the_trace
       end
 
@@ -332,17 +337,15 @@ describe Ci::API::Builds do
 
         context 'when project for the build has been deleted' do
           let(:build) do
-            result = create(:ci_build,
-                            :pending,
-                            :trace,
-                            runner_id: runner.id,
-                            pipeline: pipeline)
-            result.project.update(pending_delete: true)
-            result
+            attributes = {runner_id: runner.id, pipeline: pipeline}
+            create(:ci_build, :pending, :trace, attributes) do |build|
+              build.run
+              build.project.update(pending_delete: true)
+            end
           end
 
           it 'responds with forbidden' do
-            expect(response.status).to eq 403
+            expect(response.status).to eq(403)
           end
         end
       end