merge to 5.1, adopt testprg to optimized node recovery


storage/ndb/include/kernel/signaldata/LqhKey.hpp:
  Add Restore as friend
storage/ndb/src/kernel/blocks/restore.cpp:
  Give proper error message on LQHKEYREF
storage/ndb/test/ndbapi/testNodeRestart.cpp:
  post merge fix, adopt to optimized node recovery...