kola/tests/ignition: clean up SetHostname
kola/tests/ignition: clean up SetHostname

glevand/coreos--mantle,glevand/coreos--mantle,mjg59/mantle,mischief/mantle,dm0-/mantle,marineam/mantle,mjg59/mantle,quantum/coreos-mantle,mischief/mantle,marineam/mantle,quantum/coreos-mantle,dm0-/mantle