title: CloudBuild jobs not executed in parallel
body: <p>I am learning CloudBuild and understand that I can use <code>waitFor</code> to influence the order in which my build runs. <code>job1</code> includes some sleep time to simulate a long running job. <code>job2</code> just echos something. <code>done</code> waits for <code>job1</code> &amp; <code>job2</code>. So I created a test build like this: I have a <code>package.json</code></p>
  
  <pre><code>{
    "scripts": {
      "job1": "echo \"[job1] Starting\" &amp;&amp; sleep 5 &amp;&amp; echo \"[job1] ...\" &amp;&amp; sleep 2 &amp;&amp; echo \"[job1] Done\" &amp;&amp; exit 0",
      "job2": "echo \"[job2] Hello from NPM\" &amp;&amp; exit 0",
      "done": "echo \"DONE DONE DONE!\" &amp;&amp; exit 0"
    },
  }
  </code></pre>
  
  <p>Job 1 simulates a long running job, where I was hopping job 2 will execute in parallel. But seems like the output shows its not. Does CloudBuild run 1 step at a time only? </p>
  
  <p><code>cloudbuild.yaml</code></p>
  
  <pre><code>steps:
  - name: 'gcr.io/cloud-builders/npm'
    args: ['run', 'job1']
    id: 'job1'
  - name: 'gcr.io/cloud-builders/npm'
    args: ['run', 'job2']
    id: 'job2'
  - name: 'gcr.io/cloud-builders/npm'
    args: ['run', 'done']
    waitFor: ['job1', 'job2']
  </code></pre>
  
  <p><strong>Output</strong></p>
  
  <pre><code>Operation completed over 1 objects/634.0 B.                                      
  BUILD
  Starting Step #0 - "job1"
  Step #0 - "job1": Already have image (with digest): gcr.io/cloud-builders/npm
  Step #0 - "job1": 
  Step #0 - "job1": &gt; learn-gcp@1.0.0 job1 /workspace
  Step #0 - "job1": &gt; echo "[job1] Starting" &amp;&amp; sleep 5 &amp;&amp; echo "[job1] ..." &amp;&amp; sleep 2 &amp;&amp; echo "[job1] Done" &amp;&amp; exit 0
  Step #0 - "job1": 
  Step #0 - "job1": [job1] Starting
  Step #0 - "job1": [job1] ...
  Step #0 - "job1": [job1] Done
  Finished Step #0 - "job1"
  Starting Step #1 - "job2"
  Step #1 - "job2": Already have image (with digest): gcr.io/cloud-builders/npm
  Step #1 - "job2": 
  Step #1 - "job2": &gt; learn-gcp@1.0.0 job2 /workspace
  Step #1 - "job2": &gt; echo "[job2] Hello from NPM" &amp;&amp; exit 0
  Step #1 - "job2": 
  Step #1 - "job2": [job2] Hello from NPM
  Finished Step #1 - "job2"
  Starting Step #2
  Step #2: Already have image (with digest): gcr.io/cloud-builders/npm
  Step #2: 
  Step #2: &gt; learn-gcp@1.0.0 done /workspace
  Step #2: &gt; echo "DONE DONE DONE!" &amp;&amp; exit 0
  Step #2: 
  Step #2: DONE DONE DONE!
  Finished Step #2
  PUSH
  DONE
  </code></pre>