I meet Joan Burton on a bright cold weekday morning in Blanchardstown, where she’s fresh from canvassing at the train station. She gives the impression of enjoying the buzz. She’s full of chat with constituents and when we talk, she presses Labour’s message with enthusiasm. As former leader of the party and former Tánaiste, she’s a forceful voice. Labour is short of them. The party lost 30 of its 37 seats in the 2016 election. The ones left behind are party veterans. She is using the finance spokesperson job to push Labour’s overall agenda, rather than to audition for the…