uorb callbacks: fix unregister ordering to avoid race conditions

The order should be: first unregister, then remove the item from the
runnable queue.

src/lib/mixer_module/mixer_module.cpp

@@ -126,8 +126,8 @@ bool MixingOutput::updateSubscriptions(bool allow_wq_switch)
 
 	if (_scheduling_policy == SchedulingPolicy::Auto) {
 		// first clear everything
-		_interface.ScheduleClear();
 		unregister();
+		_interface.ScheduleClear();
 
 		// if subscribed to control group 0 or 1 then move to the rate_ctrl WQ
 		const bool sub_group_0 = (_groups_required & (1 << 0));

src/modules/sensors/vehicle_acceleration/VehicleAcceleration.cpp

@@ -71,14 +71,14 @@ bool VehicleAcceleration::Start()
 
 void VehicleAcceleration::Stop()
 {
-	Deinit();
-
 	// clear all registered callbacks
 	for (auto &sub : _sensor_sub) {
 		sub.unregisterCallback();
 	}
 
 	_sensor_selection_sub.unregisterCallback();
+
+	Deinit();
 }
 
 void VehicleAcceleration::CheckFilters()

src/modules/sensors/vehicle_angular_velocity/VehicleAngularVelocity.cpp

@@ -74,14 +74,14 @@ bool VehicleAngularVelocity::Start()
 
 void VehicleAngularVelocity::Stop()
 {
-	Deinit();
-
 	// clear all registered callbacks
 	for (auto &sub : _sensor_sub) {
 		sub.unregisterCallback();
 	}
 
 	_sensor_selection_sub.unregisterCallback();
+
+	Deinit();
 }
 
 void VehicleAngularVelocity::CheckFilters()

src/modules/sensors/vehicle_imu/VehicleIMU.cpp

@@ -66,11 +66,11 @@ bool VehicleIMU::Start()
 
 void VehicleIMU::Stop()
 {
-	Deinit();
-
 	// clear all registered callbacks
 	_sensor_accel_integrated_sub.unregisterCallback();
 	_sensor_gyro_integrated_sub.unregisterCallback();
+
+	Deinit();
 }
 
 void VehicleIMU::ParametersUpdate(bool force)