fix obvious errors when NetworkManager is missing #551

Job	Run time
containers (mypy)	2m 58s
containers (doc)	1m 10s
containers (pep8)	1m 34s
containers (pylama)	59s
containers (pytest_centos_stream8)	1m 29s
containers (pytest_debian_buster)	1m 21s
containers (pytest_debian_bullseye)	1m 37s
containers (pytest_fedora_36)	1m 30s
containers (pytest_fedora_37)	1m 49s
containers (pytest_ubuntu_bionic)	1m 6s
containers (pytest_ubuntu_focal)	3m 28s
	19m 1s

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