master: Clean up code in chunks.cc

This commit removes the following preprocessor definitions

  #define USE_SLIST_BUCKETS 1
  #define USE_FLIST_BUCKETS 1
  #define USE_CHUNK_BUCKETS 1

and removes all ifdefs which use then as if they were defined. This
doesn't change anything, but makes some code more clear, eg. the
function chunk_term.

Change-Id: If33a05f017717700b82cf98808929da15aac70e9