The “Legacy” setting should not exists in 2.1 please take a look at you host tag definition. You should see there a message that this an obsolete/faulty tag entry since 1.6.
The Check_MK service must appear if you set something different than “no agent” and “no snmp”.
If one of booth settings have anything else than the “no” setting the service must be there.
Before the upgrade where started not all old obsolete settings where removed.