labs: rename local vars: functions.guest
labs: rename local vars: functions.guest

Make local variables lowercase and some of them more descriptive.

Change-Id: Id170dcf5cccc11b2d156e09018b683b686a9764d

harrisonfeng/training-guides,Nabs007/training-guides,harrisonfeng/training-guides,harrisonfeng/training-guides,openstack/training-guides,openstack/training-guides,Nabs007/training-guides,Nabs007/training-guides