A self-described soldier of fortune who was to have testified about arms shipments to Nicaraguan contras died of an accidental cocaine overdose and there was no evidence of foul play, the county coroner's office said. Steven Paul Carr, 27, died Dec. 13 outside the Panorama City town house where he rented a room. Coroner's spokesman Dean Gilmour said Carr was "known to have been using cocaine continuously during the three days prior to this death." Carr had told FBI investigators looking into allegations of wrongdoing by the Nicaraguan rebels and some of their American backers that he had helped deliver weapons to them and was to testify in Miami. Carr, who moved to Panorama City in mid-November, told his landlord that he had received death threats.