Add motor_inertia to NMotor

Change-Id: I75b164e5a5be06af9f13903fde6fa02ceca35bd0
diff --git a/frc971/control_loops/python/control_loop.py b/frc971/control_loops/python/control_loop.py
index ac22821..8bd70fe 100644
--- a/frc971/control_loops/python/control_loop.py
+++ b/frc971/control_loops/python/control_loop.py
@@ -598,6 +598,7 @@
         self.resistance = motor.resistance / n
         self.Kv = motor.Kv
         self.Kt = motor.Kt
+        self.motor_inertia = motor.motor_inertia * n
 
 
 class Vex775Pro(object):