By Leika Kihara TOKYO, May 19 (Reuters) - Financial market turbulence could force the Bank of Japan to go slow on the unwinding of its massive debt holdings, giving anxious bond investors some relief as surging yields lay bare worsening fiscal strains and inflation pressures. The central bank sets a high bar for outright bond market intervention, said three sources familiar with the BOJ's ‌thinking, but it could flag a slowdown or pause in its so-called quantitative tightening plans for next fiscal year ...