service: Add unit test for HealthCheckNodePort=false
service: Add unit test for HealthCheckNodePort=false

When HealthCheckNodePort is false, then the service health server will
be nil. This commit adds a unit test to ensure that the code does not
crash if the service health server is nil.

Signed-off-by: Sebastian Wicki <db043b2055cb3a47b2eb0b5aebf4e114a8c24a5a@isovalent.com>

cilium/cilium,cilium/cilium,michi-covalent/cilium,michi-covalent/cilium,michi-covalent/cilium,tgraf/cilium,tgraf/cilium,cilium-team/cilium,michi-covalent/cilium,cilium/cilium,tklauser/cilium,tklauser/cilium,tgraf/cilium,cilium-team/cilium,tgraf/cilium,tgraf/cilium,tklauser/cilium,michi-covalent/cilium,cilium/cilium,tgraf/cilium,tklauser/cilium,tklauser/cilium,cilium/cilium