endpoint: Only remove failure directory after successful build
endpoint: Only remove failure directory after successful build

This is a little bit more consistent as it gurantees for a failure directory to
continue to exist until a new build succeeds and can be moved in place.

Signed-off-by: Thomas Graf <5f50a84c1fa3bcff146405017f36aec1a10a9e38@cilium.io>

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