fixes for ndb_* tests broken by previous fix

be more careful in ndb about setting errors on failure of info call (especially
in open) 


sql/ha_ndbcluster.cc:
  fix some ndb* tests failing due to fix for 19914
  
  be more careful about setting errors on failure of info call
sql/ha_ndbcluster.h:
  fix some ndb* tests failing due to fix for 19914
  
  be more careful about setting errors on failure of info call