title: Sonar Quality Gate behavior in Jenkins pipeline is unstable
body: <p>I have some pipelines in Jenkins, with the SonarQube stage (Version: 6.7.1, build 35068).
  In some builds it is aborted due to time out:</p>
  
  <pre><code>12:19:01 Sleeping for 3 min 0 sec
  [Pipeline] timeout
  12:22:10 Timeout set to expire in 25 min
  [Pipeline] waitForQualityGate
  12:22:10 Checking status of SonarQube task 'XXXXXXXXX' on server 'Sonar'
  12:22:10 SonarQube task 'XXXXXXXXXX' status is 'PENDING'
  12:47:10 Cancelling nested steps due to timeout
  </code></pre>
  
  <p>and in some other builds it pass:</p>
  
  <pre><code>13:56:47 Sleeping for 3 min 0 sec
  [Pipeline] timeout
  13:59:47 Timeout set to expire in 25 min
  [Pipeline] {
  [Pipeline] waitForQualityGate
  13:59:47 Checking status of SonarQube task 'XXXXXXXXXX' on server 'Sonar'
  13:59:47 SonarQube task 'XXXXXXXXXXXX' status is 'SUCCESS'
  13:59:47 SonarQube task 'XXXXXXXXXXXX' completed. Quality gate is 'WARN'
  </code></pre>
  
  <p>what might be the reason for it? how can I keep it stable? can it be network issue?</p>