uorb tests: run at max priority & increase stack size

- running at max priority significantly decreases jitter for the latency
  test, providing more consistent results
- stack size increase is required for the latency test

src/modules/uORB/uORB_tests/CMakeLists.txt

@@ -44,6 +44,7 @@ px4_add_module(
 	MODULE modules__uORB__uORB_tests
 	MAIN uorb_tests
 	STACK_MAIN 2048
+	PRIORITY "SCHED_PRIORITY_MAX"
 	COMPILE_FLAGS
 	SRCS ${SRCS}
 	DEPENDS

src/modules/uORB/uORB_tests/uORBTest_UnitTest.hpp

@@ -146,8 +146,8 @@ int uORBTest::UnitTest::latency_test(orb_id_t T, bool print)
 	// prevent access if the caller data goes out of scope
 	int pubsub_task = px4_task_spawn_cmd("uorb_latency",
 					     SCHED_DEFAULT,
-					     SCHED_PRIORITY_MAX - 5,
-					     1500,
+					     SCHED_PRIORITY_MAX,
+					     1700,
 					     (px4_main_t)&uORBTest::UnitTest::pubsubtest_threadEntry,
 					     args);