[examples] Zero motors on disabledInit() in sim physics examples (#2906)

This ensures that mechanisms will stop moving if the robot is disabled while motors are in motion

wpilibjExamples/src/main/java/edu/wpi/first/wpilibj/examples/statespacedifferentialdrivesimulation/Robot.java

@@ -55,5 +55,6 @@ public class Robot extends TimedRobot {
   @Override
   public void disabledInit() {
     CommandScheduler.getInstance().cancelAll();
+    m_robotContainer.zeroAllOutputs();
   }
 }

wpilibjExamples/src/main/java/edu/wpi/first/wpilibj/examples/statespacedifferentialdrivesimulation/RobotContainer.java

@@ -77,6 +77,13 @@ public class RobotContainer {
     return m_robotDrive;
   }
 
+  /**
+   * Zeros the outputs of all subsystems.
+   */
+  public void zeroAllOutputs() {
+    m_robotDrive.tankDriveVolts(0, 0);
+  }
+
   /**
    * Use this to pass the autonomous command to the main {@link Robot} class.
    *