ostest:Fix the issue that nxevent pthread was not executed, causing case failed

Summary:
  In the case of slow overall system response (such as when MM_KASAN is turned on), the nxevent case work thread will not be executed and will be switched back to the main thread, so that the event does not get the expected result and the case fails.
By adjusting the thread priority, the work thread can be scheduled to avoid the expected result failure

Signed-off-by: chenrun1 <[email protected]>

Author: crafcat7

testing/ostest/nxevent.c

@@ -281,7 +281,7 @@ void nxevent_test(void)
 
   /* Lower priority */
 
-  sparam.sched_priority = PTHREAD_DEFAULT_PRIORITY - 1;
+  sparam.sched_priority = PTHREAD_DEFAULT_PRIORITY;
   pthread_attr_setschedparam(&attr, &sparam);
 
   /* Create thread */
@@ -304,7 +304,7 @@ void nxevent_test(void)
 
   /* Lower priority */
 
-  sparam.sched_priority = PTHREAD_DEFAULT_PRIORITY - 1;
+  sparam.sched_priority = PTHREAD_DEFAULT_PRIORITY;
   pthread_attr_setschedparam(&attr, &sparam);
 
   /* Create thread */