Remove LiveUpdate params

The params were added in I2997d23c584055c40034827e9beb58e6542ea11c
as a means to pass undercloud image data to overcloud instances
so they could perform an update via takeovernode). We've
never actually made use of them via takeovernode... furthermore
these params are a bit stale in that they haven't been applied
to other instance types (storage, etc.).

I propose we remove them entirely and start with a fresh plan for
how these would get used (perhaps a blueprint).  As is these don't
appear to have ever been fully wired up to do anything removing
them should have no effect on end users.

Change-Id: I96f91fb0d67e7fe203d3767c8ab89ce82adbe331
Merge "Remove LiveUpdate params"