Some CNIs such as OVN don't use kubeproxy and provide
there own implementation for network proxy .
This patch allow to disable the kubeproxy start in the
local-up-cluster.sh script.

It is also move the generation of the certificate and
kubeconfig to  start_kubeproxy function so it will be
generated only when it needed.

This is useful for us for developement and CI testing.
Signed-off-by: Moshe Levi <moshele@mellanox.com>