image-desc: Don't forget to declare external @fdset_template

While being extracting common part of image descriptors to separate file
this declaration escaped me.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

include/image-desc.h

@@ -90,4 +90,6 @@ struct cr_fd_desc_tmpl {
 	void		(*show)(int fd);
 };
 
+extern struct cr_fd_desc_tmpl fdset_template[CR_FD_MAX];
+
 #endif /* __CR_IMAGE_DESC_H__ */