use m_cofigMutex when configuration is accessed
   use c++ iteration interface everywhere in MgmtSrvr code
    use NDB_INVALID_SOCKET everywhere in Services.cpp


ndb/src/common/transporter/TransporterRegistry.cpp:
  removed warning
ndb/src/mgmapi/mgmapi.cpp:
  mgmapi to return connected port and interface _only_ if it is actually connected
ndb/src/mgmsrv/MgmtSrvr.cpp:
  use m_cofigMutex when configuration is accessed
  use c++ iteration interface everywhere
ndb/src/mgmsrv/Services.cpp:
  use NDB_INVALID_SOCKET everywhere