CA-142595: Add one unit test + remove unused code in another test

Signed-off-by: Flavien Quesnel <flavien.quesnel@citrix.com>
CA-142595: Rename devscan._get_block_device_name to show it is kernel 3.x specific

Signed-off-by: Flavien Quesnel <flavien.quesnel@citrix.com>