data/eval/_multistage_traineval.sh: Use phase-specific barriers
data/eval/_multistage_traineval.sh: Use phase-specific barriers

I just encountered a case where phase 2 went through too quickly in training and the testing got stuck on a barrier forever.

Martinfx/yodaqa,Martinfx/yodaqa,Martinfx/yodaqa,vineetk1/yodaqa,vineetk1/yodaqa,Martinfx/yodaqa,vineetk1/yodaqa,Martinfx/yodaqa,vineetk1/yodaqa,Martinfx/yodaqa,vineetk1/yodaqa,vineetk1/yodaqa