Test Failing: Virtualbox error?

Job link: https://logstash-ci.elastic.co/job/elastic+logstash+6.0+multijob-acceptance/label=metal,suite=debian/54/console
```
20:51:12 Stderr: VBoxManage: error: The machine 'qa_debian-8_1506545469118_1066' is already locked by a session (or being locked or unlocked)
20:51:12 VBoxManage: error: Details: code VBOX_E_INVALID_OBJECT_STATE (0x80bb0007), component MachineWrap, interface IMachine, callee nsISupports
20:51:12 VBoxManage: error: Context: "LaunchVMProcess(a->session, sessionType.raw(), env.raw(), progress.asOutParam())" at line 590 of file VBoxManageMisc.cpp
20:51:12 /var/lib/jenkins/workspace/elastic+logstash+6.0+multijob-acceptance/label/metal/suite/debian/qa/vagrant/command.rb:49:in `run!'
20:51:12 /var/lib/jenkins/workspace/elastic+logstash+6.0+multijob-acceptance/label/metal/suite/debian/qa/vagrant/helpers.rb:21:in `bootstrap'
20:51:12 /var/lib/jenkins/workspace/elastic+logstash+6.0+multijob-acceptance/label/metal/suite/debian/qa/Rakefile:40:in `block in (root)'
20:51:12 /var/lib/jenkins/.rbenv/versions/jruby-9.1.12.0/bin/bundle:22:in `'
```