LPS-43902

Hey Hugo,

Basically, this fix is just making it so that we do not generate a screenname for a user that already has one.

Note from George:

As mentioned on the LPS:

"In 6.1.30, 6.1.x, AND master, screennames are not permanently set. I have tested this with LDAP configured and screennames set to auto-generated, and I can verify that screennames are changing after logging in and logging out."