Fix "nagios-install" reference in allinone help
Fix "nagios-install" reference in allinone help

The help output for --allinone refers to --install-nagios=y,
but it should be --nagios-install=y.

Change-Id: I53ea43bc5be52fe26e962633e991f80ca6528f0a

bcrochet/packstack,openstack/packstack,spkane/packstack,paramite/packstack,pkilambi/packstack,stackforge/packstack,harveyzh/packstack,bcrochet/packstack,weshayutin/packstack,openstack/packstack,paramite/packstack,pkilambi/packstack,derekhiggins/packstack,openstack/packstack,alincalinciuc/packstack,radez/packstack,imcsk8/packstack,palmer159/openstack-test,paramite/packstack,stackforge/packstack,mahak/packstack,palmer159/openstack-test,weshayutin/packstack,derekhiggins/packstack,fr34k8/packstack,fr34k8/packstack,bcrochet/packstack,xbezdick/packstack,larsks/packstack,stackforge/packstack,imcsk8/packstack,imcsk8/packstack,harveyzh/packstack,larsks/packstack,spkane/packstack,larsks/packstack,palmer159/openstack-test,alincalinciuc/packstack,harveyzh/packstack,derekhiggins/packstack,fr34k8/packstack,alincalinciuc/packstack,radez/packstack,pkilambi/packstack,mahak/packstack,spkane/packstack,mahak/packstack,xbezdick/packstack,radez/packstack,weshayutin/packstack,xbezdick/packstack