Improve hdfio output test (when ite==-1)

HySoP/hysop/operator/hdf_io.py

@@ -208,7 +208,7 @@ class HDF_Writer(HDF_IO):
         if simulation is None:
             raise ValueError("Missing simulation value for monitoring.")
         ite = simulation.currentIteration
-        if ite % self.io_params.frequency == 0:
+        if ite == -1 or ite % self.io_params.frequency == 0:
             self.step(simulation)
             self._count += 1