refactor keystone.conf template specs

add tests for every tunable.  organize code layout to reflect actual
template layout (group tests, in order).  also 3x performance gain by
collapsing 50+ chef converges into one.  remove 'pending' tests in
other platforms since there are no platform-specific tunables.

Change-Id: Ib0dc3728a5b0c81bf3b3a36a1a644a7a2fff5910
Closes-Bug: #1182562