Explicitly set keystone auth_strategy

Explicitly set keystone as the auth_strategy. Also moved sysctl
load command closer to where the related config changes
actually appear.

Closes-Bug: #1258295
backport: havana
Change-Id: I8ae977c8eac984c2f56b9318b6369e02847546d1
(cherry picked from commit ec5d0950104f65fdc55e8e8e6821358982bcd293)
Install Guide: Use OS_* for variables

The variables are now OS_SERVICE..., change them.

Change-Id: I945506fe943d58116456c4dbffb343a29403bf4c
backport: havana
(cherry picked from commit dbf33a84014d4001bb45802064d55d2a74616b55)
Merge "Install Guide: Use OS_* for variables" into stable/havana
Merge "Explicitly set keystone auth_strategy" into stable/havana