docs: use %H instead of a hardcoded IP
docs: use %H instead of a hardcoded IP

In https://coreos.com/docs/launching-containers/launching/launching-containers-fleet/
Run a Simple Sidekick, it uses %H.  Not sure why it would be using a
hardcoded ip rather than %H.

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