eni: Fix ForeachInterface if InstanceID is not known
eni: Fix ForeachInterface if InstanceID is not known

Fix ForeachInterface to not return all ENIs if the instanceID is not
known. None of the callers expect this behavior and if the instanceID is
not known for some reason (for example due to the recent bug in 1.7 <->
1.8 compatibility handling), then all ENIs are iterated over instead of
just the ENI of the desired instance.

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

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