Queensland Performing Arts Centre, Brisbane, May 17 and 18 (matinee) Old politicians are never the ones who die in battle, are they? Jiří Kylián’s Soldier’s Mass (1980) isn’t the only ballet to illustrate that poignant truth but it is one of the most affecting. With Bohuslav Martinů’s anguished Field Mass (1939) ringing in their ears, 12 young…