Two weekends ago, when music and theatrical performances everywhere began to topple like dominoes, Katie Jones, the artistic director of Asheville’s Magnetic Theatre , spoke with the cast and crew about to premiere the play “Traitor.” “It was late Thursday night, and this particular group had been through their dress rehearsal,” Jones said. “They’ve done a whole production’s worth of work and I thought ‘OK, if we don’t do this production now, we’re never gonna get to do it.’” Opening night was