D3PDMakerCoreComps: Fix for getting DVLInfo.

May need to explicitly call dvlinfo() on the DV class to get
the DVLInfo object registered.

PhysicsAnalysis/D3PDMaker/D3PDMakerCoreComps/src/SGDataVectorGetterTool.cxx

 /*
-  Copyright (C) 2002-2017 CERN for the benefit of the ATLAS collaboration
+  Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
 */
 
 // $Id: SGDataVectorGetterTool.cxx 790090 2016-12-16 05:31:29Z ssnyder $
@@ -79,6 +79,13 @@ StatusCode SGDataVectorGetterTool::initialize()
       meth.Execute();
     m_info = getInfo (typeinfo());
   }
+  if (!m_info) {
+    TClass* cls = gROOT->GetClass (m_typename.c_str());
+    TMethodCall meth (cls, "dvlinfo", "");
+    if (meth.IsValid())
+      meth.Execute();
+    m_info = getInfo (typeinfo());
+  }
 
   if (!m_info) {
     REPORT_MESSAGE (MSG::ERROR)