Bug #26997  	mysqld segfault when in single user mode


sql/ha_ndbcluster.cc:
  make sure error is always set even if no proper error code from ndb
storage/ndb/src/ndbapi/NdbDictionaryImpl.cpp:
  add error code for failing send signal (typically single user mode)
storage/ndb/src/ndbapi/ndberror.c:
  added error code for failing send signal and timeout waiting for node failure