Disallow using __tenantt_id__ label if source_tenants has less than 2 tenants

[FUSAKLA]

The __tenant_id__ is added to federated queries only if there are more than 2 tenants in the X-Scope-OrgID HTTP header

This happens only if the rule group source_tenants is set to more than one distinct tenants.

If not, you should not use the __tenant_id__ label in the queries