Fifty years after Fleetwood Mac shook up music with its glistening California folk-pop, two members team up on an LP of duets. In many ways, it’s still quintessential Fleetwood Mac; the songs were recorded in the band’s old L.A. studio with support from Mick Fleetwood and John McVie, and have the same jangles and harmonies that soundtracked the ‘70s. But Buckingham and McVie find room to play, from stripped-down guitar in “Love Is Here to Stay” to blustery drums in “Too Far Gone.”