operator: Add sync.Once for k8s node watcher
operator: Add sync.Once for k8s node watcher

This is to make sure that k8s node watcher is only setup at max once.
Also, synced channel is added, so that the consumer of this store
knows if syncing process is done.

Signed-off-by: Tam Mach <2524536bcff1dac29d2f6b38b02eb7c94efb5019@isovalent.com>

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