Mavis Staples, James Taylor, The Eagles, Al Pacino at a bittersweet Kennedy Center Honors 2016

WASHINGTON — Rocker Glenn Frey died before he could accept a Kennedy Center Honors award last year, but his Eagles bandmates and four other artists were feted Sunday at a bittersweet edition of the glitzy annual gala, the last of the Obama administration. Actor-director Al Pacino, singer-songwriter James Taylor, singer Mavis Staples and pianist Martha Argerich…