Add support for running as a init sidecar container (#99)

Adds support for injecting the client as a [sidecar
container](https://kubernetes.io/docs/concepts/workloads/pods/sidecar-containers/)
using the `netbird.io/init-sidecar: "true"` pod annotation.

cmd/main.go

@@ -105,7 +105,6 @@ func main() {
 		"",
 		"Default labels used for all resources, in format key=value,key=value",
 	)
-
 	// Controller generic flags
 	var (
 		metricsAddr          string