util/uuid: Add UUID_STR_LEN definition

qemu_uuid_unparse() includes a trailing NUL when writing the uuid
string and the buffer size should be UUID_FMT_LEN + 1 bytes. Add a
define for this size and use it where required.

Cc: Fam Zheng <fam@euphon.net>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: "Denis V. Lunev" <den@openvz.org>
Signed-off-by: Cédric Le Goater <clg@redhat.com>

util/uuid.c

@@ -51,7 +51,7 @@ int qemu_uuid_is_equal(const QemuUUID *lhv, const QemuUUID *rhv)
 void qemu_uuid_unparse(const QemuUUID *uuid, char *out)
 {
     const unsigned char *uu = &uuid->data[0];
-    snprintf(out, UUID_FMT_LEN + 1, UUID_FMT,
+    snprintf(out, UUID_STR_LEN, UUID_FMT,
              uu[0], uu[1], uu[2], uu[3], uu[4], uu[5], uu[6], uu[7],
              uu[8], uu[9], uu[10], uu[11], uu[12], uu[13], uu[14], uu[15]);
 }