Add non-configurable attribute for http/https use in keystone [6/7]

In short: this doesn't change the current behavior, and is only a
preparatory commit for future SSL support in keystone.

This is set to http right now; this will enable other barclamps to use
this attribute without breaking them, and then we can make this
configurable.

Crowbar-Pull-ID: 4572857ca9291f4fab46772cbbe8ff0a06969160

Crowbar-Release: pebbles