Added missing DBUG enter, compiled and tested on production with debug-max
  build (my regular build missed the previous errors friday)

Changeset:
 Added missing DBUG_ENTER, compiled and tested on production with debug-max
 build!



sql/ha_blackhole.cc:
  Added missing DBUG enter, compiled and tested on production with debug-max build (my regular build missed the previous errors friday)
  C