MDEV-4974: memory leak in 5.5.32-MariaDB-1~wheezy-log
- When a JOIN has both "optimization tabs" (JOIN_TABs used to
read the base tables and do the join operation) and also
has "execution tabs" (a JOIN_TAB that is to produce result set
that is sent to the client), do not forget to call JOIN_TAB::cleanup()
for the execution JOIN_TAB.