Handle weird disk names in get_blockdev_size

We need to allow for numbers in the disk name, and also that if
the last character is a digit, the partition name will include a 'p'
between the disk name and the partition number.

See https://bugzilla.redhat.com/show_bug.cgi?id=1006077

Signed-off-by: Andy Grover <agrover@redhat.com>
update version to 2.1.38

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