Switch from robot to pimu push command

stretch_core/nodes/stretch_driver

@@ -528,7 +528,7 @@ class StretchDriverNode:
             # odometry, and publish joint states
             while not rospy.is_shutdown():
                 self.robot.pimu.set_fan_on()
-                self.robot.push_command()
+                self.robot.pimu.push_command()
                 self.command_mobile_base_velocity_and_publish_state()
                 command_base_velocity_and_publish_joint_state_rate.sleep()
         except (rospy.ROSInterruptException, ThreadServiceExit):