cache forge modules under its own cache directory in puppetfile mode

[mmolnar]

Modules from puppet forge were being stored directly under cache directory instead of forge subdirectory in cache.

This was a difference in behaviour between config and puppetfile modes and causing forge modules to be stored 2x in cache.

[xorpaul]

You're right, trying to behave the same in puppetfile modse as in config mode is the better solution.