Geofence - Do not trigger geofence failsafe while in low battery

failsafe action.
Also move geofence flags from static variables declared into the if
statement to private members of the class.

src/modules/commander/Commander.hpp

@@ -163,6 +163,12 @@ private:
 	float		_load_factor_ratio{0.5f};	/**< ratio of maximum load factor predicted by stall speed to measured load factor */
 	float		_apsd_innov_integ_state{0.0f};	/**< inegral of excess normalised airspeed innovation (sec) */
 
+	/* geofence flags */
+	bool _geofence_loiter_on{false};
+	bool _geofence_rtl_on{false};
+	bool _warning_action_on{false};
+	hrt_abstime _last_geofence_violation{0};
+
 	FailureDetector _failure_detector;
 	bool _failure_detector_termination_printed{false};