login_failed_count_since_success isn't counted correctly

The scenario which I reproduced in my instance while I was testing on MDL-73736 (jaked found this issue and I verified it on my instance):

Steps to replicate:

1. In the config.php, add $CFG->disablelogintoken = true;
2. Create a user say testuser1
3. Try to log in with testuser1 with the incorrect password. Repeat it multiple times. You should see 'login_failed_count_since_success' incrementing.
4. Now try to log in as testuser1 with the correct credentials.
5. Now you should see that the 'login_failed_count_since_success' value in the database is not reset to zero. This is not correct.

On the other hand, if the user tries to set 'displayloginfailures' (in System Administration > Security > Notifications) to true (by ticking the check box and saving changes). Later when the user logs in with correct credentials, the 'login_failed_count_since_success' is reset to 0.