Fix a race condition in innodb_mysql.test

mysql-test/include/mix1.inc:
  Fix a race condition in the test, causing a sporadic failure.

mysql-test/include/mix1.inc

@@ -1309,6 +1309,7 @@ SELECT * FROM t1;
 
 --echo # Switch to connection con2
 connection con2;
+--reap
 SELECT * FROM t1;
 
 --echo # Switch to connection con1