devstack/lib/magnum#L184-188 was temporary work until barbican is
available, but they are still needed only for local cert manager when
barbican is not enabled.
Therefore move these lines into a location that runs only if it use
local cert manager.
By the way, remove the comments that no one need anymore and fixed
some indentations a little.
Change-Id: I74b4b82b26f6a80fd03a8055b9bd8c02715962a5