DD4hepSimulation: ah, check for not self is desirable

Should help in case when steering is defined with a name other than "SIM", then, without this, depending on the dict ordering it may be overtaken by "SIM". We don't want that.

DDG4/python/DDSim/DD4hepSimulation.py

@@ -114,7 +114,7 @@ def readSteeringFile(self):
     sFileTemp = self.steeringFile
     exec(compile(io.open(self.steeringFile).read(), self.steeringFile, 'exec'), globs, locs)
     for _name, obj in locs.items():
-      if isinstance(obj, DD4hepSimulation):
+      if isinstance(obj, DD4hepSimulation) and obj is not self:
         self.__dict__ = obj.__dict__
     self.steeringFile = os.path.abspath(sFileTemp)