kubeadm: try to reuse RunData if possible

The generation of `RunData` for init and join is relative time consuming,
the data should be shared / reused whenever possible.

Signed-off-by: Dave Chen <dave.chen@arm.com>

cmd/kubeadm/app/cmd/phases/workflow/runner.go

@@ -221,11 +221,13 @@ func (e *Runner) Run(args []string) error {
 		return errors.New(msg.String())
 	}
 
-	// builds the runner data
-	var data RunData
+	// builds the runner data if the runtime data is not initialized
+	data := e.runData
+	if data == nil {
 		if data, err = e.InitData(args); err != nil {
 			return err
 		}
+	}
 
 	err = e.visitAll(func(p *phaseRunner) error {
 		// if the phase should not be run, skip the phase.