Power off before powering on in tests

Author: urfeex

ur_robot_driver/test/test_common.py

@@ -235,6 +235,7 @@ class DashboardInterface(
     },
 ):
     def start_robot(self):
+        self._check_call(self.power_off())
         self._check_call(self.power_on())
         self._check_call(self.brake_release())