Can't handle devices that end in numbers, such as /dev/loop0

[mvollmer]

When creating a partition on /dev/loop0, it will be called /dev/loop0p1, but docker-storage-setup will wait for /dev/loop01.

It is probably not important to support loop devices (although they are useful for testing), but other devices might follow a similar labeling scheme and would cause docker-storage-setup to fail in the same way.

[rhatdan]

@rhvgoyal PTAL

[giuseppe]

I also needed this change to get test_storage.sh (https://github.com/projectatomic/atomic/blob/master/tests/integration/test_storage.sh) pass successfully on my Fedora machine. It works for me modulo the question I had in the code.