ha_statistic_increment for rpl_temporary

Problem: in some cases master send a special event to reconnecting
slave to keep slave's temporary tables (see #17284) and they still 
have references to the "old" SQL slave thread and use them to access
thread's data.

Fix: set temporary tables thread references to the actual SQL slave
thread in such cases.


mysql-test/suite/rpl/t/disabled.def:
  Fix for bug#38269: pushbuild gives valgrind error in 
  ha_statistic_increment for rpl_temporary
    - rpl_temporary test enabled.
sql/log_event.cc:
  Fix for bug#38269: pushbuild gives valgrind error in 
  ha_statistic_increment for rpl_temporary
    - if we keep slave's temporary tables after reconnect,
  set their thread pointers (->in_use) to the current SQL thread.