SMIL service should not load external DTD for XML validation
MH-13440 removes the DTD specification from the XML of a test XML file so that tests don't fail in case Opencast is built on an offline system. The reason the tests would fail is that the SMIL service would attempt to download the DTD to validate the XML file.
As the SMIL files that need to be processed by the SMIL service are generated by Opencast itself, the risk of running into problems because of the XML validation seems higher than the chance to run into problems because not validating the XML.
IMO, the SMIL service should not perform XML validation.
This was fixed in 7x I believe.