Add J and Mass to drivetrain_config

They are needed for trajectory planning.

Change-Id: I8daf4303fee347af77567b20078f597354ba2472
diff --git a/y2017/control_loops/drivetrain/drivetrain_base.cc b/y2017/control_loops/drivetrain/drivetrain_base.cc
index 6cc7822..ea985d7 100644
--- a/y2017/control_loops/drivetrain/drivetrain_base.cc
+++ b/y2017/control_loops/drivetrain/drivetrain_base.cc
@@ -42,6 +42,8 @@
 
       drivetrain::kHighGearRatio,
       drivetrain::kHighGearRatio,
+      drivetrain::kJ,
+      drivetrain::kMass,
       kThreeStateDriveShifter,
       kThreeStateDriveShifter,
       true /* default_high_gear */,