Add 2>dev/null when checking nm-cloud systemd unit #6541

Job	Run time
build / Build	6m 28s
Integration Tests (certrotation)	1m 41s
Integration Tests (etcdrestore)	1m 58s
Integration Tests (localstorage)	1m 26s
Integration Tests (startup)	6m 20s
Integration Tests (custometcdargs)	1m 0s
Integration Tests (etcdsnapshot)	7m 40s
Integration Tests (kubeflags)	6m 52s
Integration Tests (longhorn)	2m 52s
Integration Tests (secretsencryption)	2m 5s
	38m 22s

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