Multicopter attitude controller: Run at maximum priority.

This allows for a quicker update from sensors if the estimator runs at the default priority of the estimator class. If there is no direct sensor pass-through then it will wait for an estimator update.

src/modules/mc_att_control/mc_att_control_main.cpp

@@ -1362,7 +1362,7 @@ MulticopterAttitudeControl::start()
 	/* start the task */
 	_control_task = px4_task_spawn_cmd("mc_att_control",
 					   SCHED_DEFAULT,
-					   SCHED_PRIORITY_MAX - 5,
+					   SCHED_PRIORITY_MAX - 4,
 					   1700,
 					   (px4_main_t)&MulticopterAttitudeControl::task_main_trampoline,
 					   nullptr);