Fix leak in go-controller service controller's top level cache

When services are deleted, the services controller cache should also remove the service from its top level cache to avoid growing forever.

While this is not an issue in 4.13 once the lb_cache rework merges [1], the 4.12 and older branches have this problem because that rework is meant for 4.13 only.

[1]: https://github.com/ovn-org/ovn-kubernetes/pull/3387

This is the location where alreadyApplied is not deleting the removal: 
https://github.com/openshift/ovn-kubernetes/blob/cf9fb51510e1870961bf3a0f064b73536757a4f8/go-controller/pkg/ovn/controller/services/services_controller.go#L269

It should do the similar changes depicted here (currently merged upstream):
https://github.com/ovn-org/ovn-kubernetes/blob/cd78ae1af4657d38bdc41003a8737aa958d62b9d/go-controller/pkg/ovn/controller/services/services_controller.go#L322-L324

100%

1. create service -- use unique name
2. remove service
3. notice how alreadyApplied grows and never gets smaller
4. repeat

^^

alreadyApplied should not grow forever