Instead of defining almost all vars scoped to the 'all'group, we will
limit our vars scoping to the group namespace they are consumed in.
Vars that are used in 1 group are defined in the group they are used
in. This covers most service role vars.
Vars that are used in 2 groups (usually linking 2 roles communicating
with each other) are now using localhost's host_vars as a proxy. The
2 service groups will then reference hostvars['localhost']['var'].
Vars that are used in 3+ groups are left in the 'all' scoping.
Change-Id: I09cb22d51985d5f50e98030a455251cc2ea1a205
85501cbf26