Fix subsequent SAML sign ins
What does this MR do?
Fixes a bug when auto_link_ldap_user
is true
that causes SAML users to be unable to sign in a second time.
Are there points in the code the reviewer needs to double check?
Do we need any other tests in o_auth/user_spec.rb
Why was this MR needed?
Fix the problem for https://gitlab.zendesk.com/agent/tickets/22546