rwlock trylock functions were wrongly returning EAGAIN instead of EBUSY

src/thread/pthread_rwlock_tryrdlock.c

@@ -7,7 +7,7 @@ int pthread_rwlock_tryrdlock(pthread_rwlock_t *rw)
 		a_dec(&rw->_rw_readers);
 		if (rw->_rw_waiters && !rw->_rw_readers)
 			__wake(&rw->_rw_readers, 1, 0);
-		return EAGAIN;
+		return EBUSY;
 	}
 	return 0;
 }