[io vview] fix visibility of actors with len(contactors)>1
[io vview] fix visibility of actors with len(contactors)>1

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