k8s: Fallback to API probing if discovery API is not available
k8s: Fallback to API probing if discovery API is not available

Discovery of API groups requires the API services of the apiserver to be
healthy. Such API services can depend on the readiness of regular pods
which require Cilium to function correctly. By treating failure to
discover API groups as fatal, a critial loop can be entered in which
Cilium cannot start because the API groups can't be discovered and th
API groups will only become discoverable once Cilium is up.

Warn about the lack of discovery ability and fall back to probing the
API directly.

Signed-off-by: Thomas Graf <5f50a84c1fa3bcff146405017f36aec1a10a9e38@cilium.io>

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