Remove SWRaid method as it is no longer needed (#678379)

Active Linux software RAID devices are detected in the
Proc_Partitions_Info method.  Hence the SWRaid method is no longer
required.

Removal of the SWRaid method fixes the problem with the error message:

  Could not stat device /dev/md/0 - No such file or directory

This fixes the problem because we no longer use "mdadm --examine
--scan" in an attempt to detect Linux software RAID devices.  The
mdadm command was returning device names such as /dev/md/0, which are
incorrect for GParted.

NOTE:  With this change, GParted no longer requires the mdadm command
       to detect Linux software RAID devices.

Closes Bug #678379 - Could not stat device /dev/md/0 - No such file or
                     directory