go-controller/endpoints: Handle all endpoint delete case.
go-controller/endpoints: Handle all endpoint delete case.

When all the endpoints backing a service is deleted, you
get a modify endpoint event (and not delete endpoint event).
So we should handle it.

Signed-off-by: Gurucharan Shetty <a1872e333d0e52644f6125da2276530f7ebe5e77@ovn.org>

shettyg/ovn-kubernetes,shettyg/ovn-kubernetes,shettyg/ovn-kubernetes