User with lowercase chars logs in as another user with uppercase chars.

Steps to reproduce:
1. Create two users with the same names and passwords, but one user should be in lowercase and another in uppercase chars. (e.g. login/pass - PETROVICH/IVANOV and petrovich/ivanov)
2. Log in as ‘petrovich’ user.

Actual result:
User logs in as ‘PETROVICH’

Expected result:
User successfully logs in as ‘petrovich’