skip invalid blocking call test on valgrind, otherwise it shouts at memleaks at abortion

tests/errorcheck/invalid_blocking_calls.c

@@ -61,6 +61,9 @@ int main(int argc, char **argv)
 {
 	int ret;
 
+	if (RUNNING_ON_VALGRIND)
+		return STARPU_TEST_SKIPPED;
+
 	ret = starpu_initialize(NULL, &argc, &argv);
 	if (ret == -ENODEV) return STARPU_TEST_SKIPPED;
 	STARPU_CHECK_RETURN_VALUE(ret, "starpu_init");