o When creating the EBR scheme, set the number of entries

o  When creating the EBR scheme, set the number of entries
   properly. Otherwise the minimum of 1 is used and you can
   only insert a single partition/slice and only at sector
   0 (index 1).
o  When adding a partition/slice, recalculate the index after
   the start and size of the partition/slice are adjusted to
   make them a multiple of the track size. Since the precheck
   method sets the index based on the start of the partition
   as provided by the user, we know that we're off by at most
   1 and adjusting the index is safe.