fix(coreos-base/coreos-init): Sync up stable and live ebuilds.

Trying on a new scheme to use an if statement so we can share the same
ebuild between live and stable ebuilds. This should help avoid letting
the two get out of sync.
Merge pull request #328 from marineam/fix-docker

fix(coreos-base/coreos-init): Sync up stable and live ebuilds.