Adaptive media thumbnail tests hang forever

• Type: Bug
• Status: Closed
• Resolution: Fixed
• Affects Version/s: Master
• Fix Version/s: 7.0.0 DXP FP35, 7.0.0 DXP SP7, 7.0.5 CE GA6, 7.0.X, 7.1.0 M1, 7.1.X, Master
• Component/s: Core Infrastructure, DM > Adaptive Media
• Labels:
  • liferay-digital-enterprise-70-sp7
  • liferay-fixpack-de-35-7010
• Branch Version/s:
  7.0.x
• Backported to Branch:
  Committed
• Git Pull Request: https://github.com/brianchandotcom/liferay-portal/pull/54068

Steps to reproduce:

1. Clone the adaptive media subrepo (git clone [e-mail]:liferay/com-liferay-adaptive-media.git).
2. Deploy it to portal (gradle clean deploy -Dbuild.profile=portal).
3. Go to adaptive-media-document-library-thumbnails-test (cd adaptive-media-document-library-thumbnails-test).
4. Run the integration tests (gradle testIntegration).

Expected: Tests pass.
Actual: Tests never finish (usually testCleanUpDeletesOnlyImageThumbnails) and the following message is printed to the logs every 60 seconds:

2018-01-03 09:57:58.453 ERROR [RMI TCP Connection(3)-192.168.40.241][ServiceProxyFactory:265] Service "com.liferay.petra.process.ProcessExecutor" is unavailable in 60000 milliseconds while setting field "_processExecutor" for class "com.liferay.portlet.documentlibrary.util.PDFProcessorImpl", will retry...

Reverting 3b322d993a3fc1541aba58e19cfd9f350b9e15bb fixes the issue.