- only force HB to data nodes
- flag for if we broadcast condition on receipt of HB


ndb/src/mgmsrv/MgmtSrvr.cpp:
  Add get_connected_ndb_nodes to check status for connected data nodes only
ndb/src/mgmsrv/MgmtSrvr.hpp:
  add prototype for get_connected_ndb_nodes
ndb/src/mgmsrv/Services.cpp:
  only force HB to NDBD nodes
ndb/src/ndbapi/ClusterMgr.cpp:
  flag to control if we send the condition
ndb/src/ndbapi/ClusterMgr.hpp:
  flag for if we broadcast condition on receipt of hb