[io] mechanics_run.py: fix numerics output value in hdf5 log
[io] mechanics_run.py: fix numerics output value in hdf5 log

radarsat1/siconos,radarsat1/siconos,radarsat1/siconos,siconos/siconos,radarsat1/siconos,radarsat1/siconos,siconos/siconos,siconos/siconos,siconos/siconos