Fixed a couple S0-fixed/S0==Sn related cases

 Changed ODIDUtil.offsets_within_time_range() to consider an implicit time-0
  index entry. This allows time-seek requests with "0-" ranges to be
  processed properly.

 Fixed a bug in ODIDUtil.offsets_within_time_range() to only include the
  a DLNAAvailableSeekRangeResponse when the sim is in active state and
  supports random access.

Tested with live-time-window unset (S0 fixed) and live-time-window set to 0
 (S0-Sn).