Remove some superfluous comments.

Remove some superfluous comments.

get_empty_volume: initialize plexes to -1 (not allocated)

remove_drive_entry:
  Remove recurse parameter (there's nothing below a drive in the hierarchy).
  Use remove_sd_entry to remove sds, don't do it ourselves.
  Log errors, don't throw rude remarks.

remove_plex_entry:
  Don't use plex->subdisks as a loop limit, it gets changed in the
     loop.  This caused some removals to only remove half the subdisks.
  Change logging of some "impossible" situations.

remove_volume_entry:
  Use remove_plex_entry to remove plexes, don't do it ourselves.

update_sd_config:
  Use set_sd_state to do the work.