test/k8sT: set imagePullPolicy for cilium/log-gatherer stable tag
test/k8sT: set imagePullPolicy for cilium/log-gatherer stable tag

cilium/log-gatherer:v1.1 is not mutable thus we don't need to always
performing a pull of that docker image from docker hub.

Fixes: a9285f49ca65 ("[CI] Move vagrant start script to separate file")
Signed-off-by: André Martins <bc9800b9d52a24cce72a73dd528afed53f10e5fc@cilium.io>

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