ndb/include/ndbapi/NdbScanOperation.hpp:
  release scan op early to save memory
ndb/src/ndbapi/NdbScanOperation.cpp:
  release scan op early to save memory
ndb/src/ndbapi/NdbTransaction.cpp:
  release scan op early to save memory
ndb/src/ndbapi/Ndblist.cpp:
  release scan op early to save memory
sql/ha_ndbcluster.cc:
  release scan op early to save memory