test/helpers: make sure that key is non-empty for running `docker logs`
test/helpers: make sure that key is non-empty for running `docker logs`

Signed-off by: Ian Vernon <ian@cilium.io>

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