BUG#21530 The ndb_mgm management client doesn't set the exit status on errors, making it

          almost useless for any kind of shell script automation.
          Now add the return value that indicates the execution whether or not success 
          for many methods.


ndb/src/mgmclient/CommandInterpreter.cpp:
  Many methods add the return value that indicates whether the execution of operatioin succeeds.
  This can make ndb_mgm management client set the exit status on errors.