- Add variable "ndbcluster_binlog_terminating" and use that to signal
the cluster binlog thread it's time to shutdown. This allows
exact control of when the thread shutdown, previous implementation 
would start shutdown of the thread as soon as the mysqld started
shutdown. Now we will shutdown cluster binlog thread 
in 'ndbcluster_binlog_end'


sql/ha_ndbcluster_binlog.cc:
  Make binlog thread shutdown controllable by using a separet variable
  to communicate the order to shutdown