Ticket/master/pup 3258 apply with enc

This is only half a fix, I suspect. It fixes broken `puppet apply` where
 * an ENC script is used
 * that ENC does not return an environment
`apply` is apparently still broken *if* an environment is chosen by the ENC script.

I'm also not sure if we really want this spec test. It's quite expensive, and the issue is so odd and specific that it appears very unlikely that we will regress in this fashion.