Users with multiple LDAP identities do not sync correctly

Zendesk issue: https://gitlab.zendesk.com/agent/tickets/25362

Some organizations set up ldapmain and ldapsecondary intending to have them failover transparently. When a user signs in with both of the LDAP servers they end up with 2 LDAP identities. For some reason, this causes Group Sync to not find the correct identity and doesn't update group membership correctly.

We see in debug logs that the correct member access hash is built but it doesn't find the identity and update the access level.