[mechanics] fix debug messages
[mechanics] fix debug messages

fperignon/siconos,fperignon/siconos,fperignon/siconos,fperignon/siconos,radarsat1/siconos,bremond/siconos,siconos/siconos,radarsat1/siconos,bremond/siconos,bremond/siconos,radarsat1/siconos,siconos/siconos,fperignon/siconos,bremond/siconos,radarsat1/siconos,radarsat1/siconos,siconos/siconos,siconos/siconos,bremond/siconos