More explicit naming of variables


ndb/include/kernel/signaldata/AlterIndx.hpp:
  Add union to indicate where master node is passed in ref
ndb/include/kernel/signaldata/BuildIndx.hpp:
  Add union to indicate where master node is passed in ref
ndb/include/kernel/signaldata/CreateIndx.hpp:
  Add union to indicate where master node is passed in ref
ndb/include/kernel/signaldata/CreateTrig.hpp:
  Add union to indicate where master node is passed in ref
ndb/include/kernel/signaldata/DropIndx.hpp:
  Add union to indicate where master node is passed in ref
ndb/src/kernel/blocks/dbdict/Dbdict.cpp:
  Set error/master node also on BuildIndxRef
ndb/src/ndbapi/NdbDictionaryImpl.cpp:
  Use masterNodeId instead of errornode