Partners HealthCare System is rethinking its expansion plans in Massachusetts as it seeks to repair relations with competing hospitals and government officials, its newly appointed chief executive said Thursday. "If we're perceived as a bully or we're perceived as arrogant through our actions, I don't want that," Dr. David Torchiana said in an interview. "We know we have to soften our external relations and get ourselves out of this place of being a miscreant in Massachusetts. It's not a place we aspire to be." Torchiana also said that Partners intends to focus on controlling medical costs by operating more efficiently and better coordinating care.