title: Gitlab webhook does not trigger a build on jenkins
body: <p>I've a group of multibranch pipeline jobs generated with the following piece groovy script:</p>
  
  <pre><code>[
        'repo1',
        'repo2',
  ].each { service -&gt;
  
    multibranchPipelineJob(service) {
  
      displayName(service)
  
      branchSources {
        git {
          remote("git@gitlab.com:whatever/${service}.git")
          credentialsId('gitlab-ssh-key')
        }
      }
  
      orphanedItemStrategy {
        discardOldItems {
          daysToKeep(0)
          numToKeep(30)
        }
      }
  
      triggers {
        periodic(5)
      }
  
    }
  }
  </code></pre>
  
  <p>and in each repo a <code>Jenkinsfile</code> that looks as follows:</p>
  
  <pre><code>#!/usr/bin/env groovy
  
  properties([
        gitLabConnection('ci@gitlab.com'),
        pipelineTriggers([
              [
                    $class               : 'GitLabPushTrigger',
                    triggerOnPush        : true,
                    triggerOnMergeRequest: true,
              ]
        ]),
        disableConcurrentBuilds(),
        overrideIndexTriggers(false)
  ])
  
  node {
  
    def sbtHome = tool name: 'sbt-0.13.15', type: 'org.jvnet.hudson.plugins.SbtPluginBuilder\$SbtInstallation'
  
    stage('Checkout') {
      checkout scm
    }
  
    stage('Build') {
      sh "'${sbtHome}/bin/sbt' clean compile"
    }
  
    stage('Test') {
      sh "'${sbtHome}/bin/sbt' test"
    }
  
    if (env.BRANCH_NAME == 'develop' || env.BRANCH_NAME == 'master') {
      stage('Publish') {
        sh "'${sbtHome}/bin/sbt' publish"
      }
    }
  }
  </code></pre>
  
  <p>It all works correctly. The <em>seeder</em> project generates all the folders from the first script and all the branches for given repo are built correctly.</p>
  
  <p>Unfortunately I've problems with triggering a build for any branch after commit + push has been made to gitlab. </p>
  
  <p>I've jenkins configured correctly - I mean the gitlab plugin, there is a connection and it all works well.  </p>
  
  <p>I've also added a webhook on the gitlab side and it also runs correctly. After a test push is sent I receive <code>200 OK</code> from jenkins and I do see in logs that scanning the branches has started and detected the changes correctly. Unfortunately the build for the changed branch does not start. Here's an extract from branch scan log: </p>
  
  <pre><code>  Checking branch ci
        ‘Jenkinsfile’ found
      Met criteria
  Changes detected: ci (a7b9ae2f930b0b10d52bb42f1ecf96a68bba4a30 → 39a4c1a65051d5e90079feec14ad22455a77c58e)
  Did not schedule build for branch: ci
  </code></pre>
  
  <p>I'm 100% sure that this not a problem with communication between my jenkins instance and gitlab account. I see the webhook being triggered after push to gitlab, I see the request being send and branch scan being run. Changes are also detected but <strong>why on earth the job isn't started?</strong> I've also read the <a href="https://github.com/jenkinsci/gitlab-plugin#pipeline-multibranch-jobs-1" rel="nofollow noreferrer">docs</a> thoroughly and have it all configured correctly. </p>
  
  <pre><code>Jenkins version: 2.150.3
  Gitlab version: 11.8.1-ee
  </code></pre>
  
  <p><strong>EDIT</strong></p>
  
  <p>It seems that after upgrading jenkins to v.2.164.1 it all started working correctly.</p>