Before this fix, the test performance_schema.relaylog would fail
with sporadic failures related to statistics on update_cond.

The reason for these failures is that thread scheduling makes
impossible to predict if instrumented conditions will be used on not.

The fix is to relax the test case, to not collect statistics about:
- wait/synch/cond/sql/MYSQL_BIN_LOG::update_cond
- wait/synch/cond/sql/MYSQL_RELAY_LOG::update_cond