The problem was that aborted_threads variable was updated
twice when a client connection had been aborted.

The fix is to refactor a code to have aborted_threads updated
only in one place.


sql/mysql_priv.h:
  Make do_command() a private function.
sql/sql_parse.cc:
  1. Make do_command() a private function;
  2. Update aborted_threads in the only one place.