functional: update usage of go-systemd
functional: update usage of go-systemd

wuqixuan/fleet,coreos/fleet,hhoover/fleet,improbable-io/fleet,mwitkow/fleet,mwitkow/fleet,jonboulle/fleet,octoblu/fleet,mwhooker/fleet,dalbani/fleet,esatterwhite/fleet,coreos/fleet,paveltiunov/fleet,webwlsong/fleet,jonboulle/fleet,mookjp/fleet,giantswarm/fleet,flandr/fleet,esatterwhite/fleet,endocode/fleet,coreos/fleet,thepwagner/fleet,bviswana101/fleet,dongsupark/fleet,giantswarm/fleet,bcwaldon/fleet,mwitkow-io/fleet,dalbani/fleet,jonboulle/fleet,WPMedia/fleet,improbable-io/fleet,bcwaldon/fleet,mischief/fleet,mischief/fleet,ecnahc515/fleet,webwlsong/fleet,mwhooker/fleet,wuqixuan/fleet,WPMedia/fleet,dalbani/fleet,hhoover/fleet,mwitkow-io/fleet,octoblu/fleet,endocode/fleet,ecnahc515/fleet,mookjp/fleet,thepwagner/fleet,giantswarm/fleet,paveltiunov/fleet,improbable-io/fleet,ecnahc515/fleet,bcwaldon/fleet,dongsupark/fleet,dongsupark/fleet,flandr/fleet,endocode/fleet,bviswana101/fleet