909495: Virt-only subscriptions are not exportable

Virt only patch for master branch

TEST
--------
git checkout master
git pull --rebase
curl https://github.com/candlepin/candlepin/pull/180.patch | git am
buildconf/script/deploy
buildr spec features="virt_only"

Then do a full unit and spec test run. The above is a quick sanity test. If it passes, move on to more extensive testing. Otherwise, just stop there.

Once this is verified it needs to merge into **master** branch.