Don't print a decimal point if returning bytes

Fractions of bytes makes no sense.

Signed-off-by: Andy Grover <agrover@redhat.com>
Remove usage of is_disk_partition

Not a differentiator in whether we can use a block device as a backstore
or not.

Signed-off-by: Andy Grover <agrover@redhat.com>
Fix info print when using block device with fileio backstore

We need to get the size from the object, since block devs won't have
a passed-in value.

Signed-off-by: Andy Grover <agrover@redhat.com>