#5722 ystem allows to add users with a deleted username

[Chamila Madusani]

Description:

system allows to add users with a deleted username in following scenario:
1. add an employee with login details. (assume that the username is chamila)
2. now delete the employee > both employee and the user details will get deleted
3. then try to add a new user with thw same username (chamila). > system allows to add the user.