drop number from cloud3-admin/ subdirectories

This will allow us to branch for Cloud 4 and then have two different branches
which are easily comparable.

However, the generated box will still have the product release number in its
name and hostname, in order to clearly distinguish between boxes corresponding
to different product releases.
Yes I know - sorry for being misleading.  What I meant was: after we force-update the `release-3` branch to point to a `master` which contains this commit, we can safely update `master` to deal with Cloud 4.  We need the force-update, otherwise this whole PR is pointless.