cilium-health: Use log.Fatal() for fatal errors
cilium-health: Use log.Fatal() for fatal errors

This just standardises the logging usage a bit more.

Signed-off-by: Joe Stringer <16a9a54ddf4259952e3c118c763138e83693d7fd@cilium.io>

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