Remove unused banner variance parameters

Once a banner has been chosen, we don't actually change banner content based on
device, country, isAnonymous, or bucket.  Removing these parameters will reduce
cache fragmentation, and reduce average time to load banners.

This patch should have no user-visible effect.

Change-Id: I1a5ba8773cd8bebcc83edfc9a25d934a3a8530e3
Merge "Remove unused banner variance parameters"