datapath: Refactor node test setup
datapath: Refactor node test setup

Combine the multiple implementations into one function that can be
updated in a single place for upcoming additional steps that are
necessary for the multiple test suites.

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

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