RFE: add fun stuff to disk output

[ryran]

Unfortunately, sosreports don't capture /sys/; however, that shouldn't stop us from conditionally enhancing the disk module output. For starters, we could print the elevator as an additional column for each disk, e.g. (mockup):

$ xsos -d
STORAGE
  Multipath:
    mpatha  130  GiB  [noop]
    mpathb  690  GiB  [noop]
  Whole Disks from /proc/partitions:
    0 disks, totaling 0 GiB (0.00 TiB)
    (4 multipath/mdraid components hidden)
    - - - - - - - - - - - - - - - - - - - - -
    Disk    Size in GiB    Elevator
    ----    -----------    --------
    sda     137            cfq
    sdb     419            deadline