Bug fix in TransSys.add_caller. Callers would be removed when adding an extra call to an already existing node call.
Bug fix in TransSys.add_caller. Callers would be removed when adding an
extra call to an already existing node call.

tinelli/kind2,tinelli/kind2,tinelli/kind2,AdrienChampion/kind2,mebsout/kind2,AdrienChampion/kind2,AdrienChampion/kind2,kind2-mc/kind2,chsticksel/kind2,mebsout/kind2,mebsout/kind2,mebsout/kind2,chsticksel/kind2,chsticksel/kind2,chsticksel/kind2,mebsout/kind2,AdrienChampion/kind2,mebsout/kind2,AdrienChampion/kind2,AdrienChampion/kind2,tinelli/kind2,AdrienChampion/kind2,mebsout/kind2,chsticksel/kind2,chsticksel/kind2,daniel-larraz/kind2,AdrienChampion/kind2,mebsout/kind2,tinelli/kind2,AdrienChampion/kind2,tinelli/kind2,mebsout/kind2