- fixed error code
- added test program run in mysql-test-run bk version


mysql-test/ndb/ndbcluster.sh:
  Bug #26490 duplicate cluster error code
  - added check for duplicate error in mysql-test run
storage/ndb/include/kernel/signaldata/CreateFilegroup.hpp:
  Bug #26490 duplicate cluster error code
  - fixed error code
storage/ndb/src/ndbapi/Makefile.am:
  Bug #26490 duplicate cluster error code
  - added test program for duplicate error messages
storage/ndb/src/ndbapi/ndberror.c:
  Bug #26490 duplicate cluster error code
  - fixed error code
storage/ndb/src/ndbapi/ndberror_check.c:
  New BitKeeper file ``storage/ndb/src/ndbapi/ndberror_check.c''