Increase buffer for sysfs path

'unacknowledged_bad_blocks' is a long name for sysfs property and it
makes sysfs path over 50 characters long. Increase buffer to the double
length of the longest path available in sysfs at the moment.

Signed-off-by: Tomasz Majchrzak <tomasz.majchrzak@intel.com>
Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>