EKF - Initialize _deadrekon_time_exceeded to true.

If no sample have been received, deadrekoning and local position should be invalid.

EKF/estimator_interface.h

@@ -492,7 +492,7 @@ class EstimatorInterface
 	innovation_fault_status_u _innov_check_fail_status{};
 
 	bool _is_dead_reckoning{false};		// true if we are no longer fusing measurements that constrain horizontal velocity drift
-	bool _deadreckon_time_exceeded{false};	// true if the horizontal nav solution has been deadreckoning for too long and is invalid
+	bool _deadreckon_time_exceeded{true};	// true if the horizontal nav solution has been deadreckoning for too long and is invalid
 	bool _is_wind_dead_reckoning{false};	// true if we are navigationg reliant on wind relative measurements
 
 	// IMU vibration and movement monitoring