btrfs-progs: Add missing close_ctree to btrfs-select-super.c

Add missing close_ctree() to btrfs-select-super.c to avoid memory leak.

Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>

btrfs-select-super.c

@@ -102,6 +102,7 @@ int main(int ac, char **av)
 	 */
 	printf("using SB copy %llu, bytenr %llu\n", (unsigned long long)num,
 	       (unsigned long long)bytenr);
+	close_ctree(root);
 	btrfs_close_all_devices();
 	return ret;
 }