test: Use log-gatherer from cilium org
test: Use log-gatherer from cilium org

The Dockerfile of log-gatherer is located at
https://github.com/cilium/log-gatherer.

The other difference is that the new log-gatherer installs iproute2.

Signed-off-by: Martynas Pumputis <6b0d31c0d563223024da45691584643ac78c96e8@lambda.lt>

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