tools/nextid: pad 0 in next test id seq number

nextid returns the next available seq number, but it doesn't pad id
number with 0, e.g.

./tools/nextid ext4
23

After the fix it returns:

./tools/nextid ext4
023

This eases the process of moving tests around in a script.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Eryu Guan <eguan@redhat.com>
1 file changed