Remove error handling for getPod to force to proceed cmdDel.

In cmdDel, CNI Spec mentioned that plugin should proceed cmdDel
without any error, hence the change removes error returning
at cmdDel.

fix #822

pkg/multus/multus.go

@@ -815,7 +815,8 @@ func CmdDel(args *skel.CmdArgs, exec invoke.Exec, kubeClient *k8s.ClientInfo) er
 
 	pod, err := getPod(kubeClient, k8sArgs, true)
 	if err != nil {
-		return err
+		// getPod may be failed but just do print error in its log and continue to delete
+		logging.Errorf("Multus: getPod failed: %v, but continue to delete", err)
 	}
 
 	// Read the cache to get delegates json for the pod