Setting Hostname from Pods on EndpointSlice to match Endpoints behavior.

This was an oversight in the initial EndpointSlice release. This update
will ensure that Endpoints and EndpointSlices use the same logic to set
the Hostname attribute.

pkg/controller/endpointslice/endpointslice_controller_test.go

@@ -280,6 +280,7 @@ func TestSyncServiceFull(t *testing.T) {
 		Protocol: protoPtr(v1.ProtocolSCTP),
 		Port:     int32Ptr(int32(3456)),
 	}}, slice.Ports)
+
 	assert.ElementsMatch(t, []discovery.Endpoint{{
 		Conditions: discovery.EndpointConditions{Ready: utilpointer.BoolPtr(true)},
 		Addresses:  []string{"1.2.3.4"},