direct_io_test: use mkstmp instead of mkostemps

mkostemps isn't present in older glibc versions, like the ones in CentOS
5.5. We don't really use any of the extra functionality of mkostemps in
this test.

Signed-off-by: Colin McCabe <colin.mccabe@dreamhost.com>

qa/workunits/direct_io_test.c

@@ -98,7 +98,7 @@ static int setup_temp_file(void)
 		return -EINVAL;
 	}
 
-	fd = mkostemps(temp_file, 0, O_WRONLY | O_TRUNC);
+	fd = mkstemp(temp_file);
 	if (fd < 0) {
 		int err = errno;
 		printf("setup_big_file: mkostemps failed with error %d\n", err);