Re-enable pion truth variables in nue sandbox
FillNueSandbox_module.cc has this:
// TEMPORARILY DISABLING CODE BELOW
// TO BE REVERTED SOON
// The code below calls sim::Particle::Daughter() which is sometimes
// busted. This will be fixed in newly produced sim files, but for
// now, just skip the storing of this info.
This is why Ji isn't seeing the pion variables filled.
The word "soon" was written 2014-03-21.
I guess we still have these bad files around, but we should revert this before we make the next set of CAFs.