The problem was that number of threads was used to calculate
max_used_connections.

The fix is to use number of active connections.


mysql-test/r/connect.result:
  Update result file.
mysql-test/t/connect.test:
  - Add a test case for Bug#35074: max_used_connections is not correct;
  - Make a test case for Bug#33507 more stable.
sql/mysqld.cc:
  Use number of connections insetad of threads
  to calculate max_used_connections.