Add -r to xargs command

-r on xargs will not run the command if the input is empty.
Otherwise the command will get run once and it will fail, though
the || true catches the error. With this the || true can be
removed.

Change-Id: I12fbe83b69de39d0cae67e337cbacf8cfab02180

tools/kubeadm-aio/kubeadm-aio-launcher.sh

@@ -23,7 +23,7 @@ sudo mount --make-shared /var/lib/kubelet
 # Cleanup any old deployment
 sudo docker rm -f kubeadm-aio || true
 sudo docker rm -f kubelet || true
-sudo docker ps -aq | xargs -l1 sudo docker rm -f || true
+sudo docker ps -aq | xargs -r -l1 sudo docker rm -f
 sudo rm -rfv \
     /etc/cni/net.d \
     /etc/kubernetes \